The Adventures of Dr. McNinja has a double invert of this trope in a scene with a ninja speaking to an Irish village for about 3 panels before it's revealed nobody understands him because he's actually speaking Japanese.
The dialogue of Anecdote of Error is all written in English, but since the setting is a Constructed World, the characters are “really” speaking Batean to each other. In later pages, even the signs are translated instead of being rendered in the constructed script.
Apricot Cookie(s)!: All the dialogue is supposed to be translated from Japanese, which is Lampshaded when they meet a tourist who asks them if they speak English.
In Arthur, King of Time and Space, Latin is represented by a Roman font, in block capitals and without "J" and "U" since the Romans didn't have them. Arthur's "accent" means the Es turn into 3s
In Blade of Toshubi, the character's languages all consist of a single word — the onomatopea of sound the animal they're based on makes. For the sake of the reader, it's rendered into English-unless someone doesn't understand, in which case, we get their native language.
Elven Lacryment has various characters of different races speaking to each other, though different races are represented with different fonts.
A Fake Affair primarily takes place in Japan, but the protagonist makes several trips to Korea. When other people speak Korean in her presence, the text turns blue because she cannot understand them. When they speak broken English to bridge the language barrier, the text is green. When the Korean love interest is in his home country without her, he is assumed to be speaking Korean even though the text does not change color.
The Fox Sister: All Korean spoken in the comic is translated to English, for the readers' convenience. Interestingly, English spoken in the comic, and not Korean, is marked by angle brackets.
Get Medieval uses the translation convention heavily, originally justified because it was first written as being about time travelers in medieval France, but now required since the creator changed them to aliens before the start of the comic. So references to Morse code, which would be wholly explicable for time travelers to make, become a shorthand for "a signal code similar to Morse code, but invented by someone else" when in the mouths of aliens. Apparently, not many readers know of the Translation Convention, as the creator has had to field complaints and comments on it frequently in her commentary and on the comment pages.
Untranslated background text, names, and setting all suggest that the characters in Girl Genius are actually speaking German and some Romanian, which has been confirmed by Word of God. (Presumably, they speak French in the Paris storyline and English in the London one.)
El Goonish Shive uses the above comic book convention for characters speaking French, Japanese and the alien language Uryuomoco.
Leif & Thorn features multiple fantasy languages all written as English and distinguished by font. Sometimes there are author's notes or fourth-wall-breaking strips addressing things in the original languages that don't exactly translate.
Sønska doesn't use singular "they", but translated-from-Sønska dialogue uses "they" for a person of unknown gender because it sounds more natural in English than a literal translation of "ze."
Linburger. Whenever a language is spoken that some characters in the scene understand, but other may not understand, the text appears as regular English, with little symbols at the beginning and end of the sentence.
The titular characters of M9 Girls! speak Spanish, and the English version of the webcomic exists only for readers' convenience. The Girls' Hispanic heritage is hinted by their names, even though the Every City setting of the comic downplays it.
MegaTokyo uses English and angle brackets, as mentioned above. There are also occasional scenes in Japanese, when the actual meaning is not as important as the fact that the viewpoint character does not understand the language.
My Impossible Soulmate: Lampshaded - Japanese protagonist Chiaki wonders how she and Redge/Nara could understand each other despite the fact Chiaki had come from another world:
"We've been talking this whole time and understanding each other. So are they really speaking Japanese? Or...what if it's the other way around? Is it possible I'm not speaking Japanese anymore? How do I not know!?"
NEXT!!! Sound of the Future: The story takes place in Japan, so all the characters are really speaking Japanese even though their dialogue is written in English. This is why characters will use Japanese honorifics like -chan and -san and use Goroawase Numbers for their codenames.
Outsider: Outside of the prologue, where the Bellarmine's crewmembers are speaking English to each other, the characters are always speaking in the Trade language. The first few panels after Jardin awakens on the Loroi ship write out the Trade dialogue in full with parenthetical translations, but a footnote explains that, after that, all dialogue will be represented by English for simplicity.
RE-man: The first few scenes are explicitly stated via footnotes to be translated from the R'Manthean dialect, and are enclosed in brackets. When RE-man crash-lands on Earth, his dialogue is definitely not English.
Scandinavia and the World: Lampshaded in this comic as an answer to a frequently asked reader question. (with additional Bilingual Bonus since the author decided to Google Translate all the text from English, even though she speaks Danish as her native language)
Sluggy Freelance sometimes plays it straight with lines that are made clear are translated from another language, but also parodies it.
In the Bikini Suicide Frisbee Days guest strips, a short story arc has the main characters gain useless Medium Awareness superpowers. Zoë becomes "Translated Girl" with everything she says said in another language but translated for the viewer.
Parodied, lampshaded and, if you think about it, subverted: In Mohkadun, one of the characters in ancient Mohkadun calls someone "smarty-pants", and then both wonder what "pants" is. (Everyone there wears tunics and stuff.) It's a subversion in that while the dialogue on the whole is obviously being shown in English while spoken in another language (there are Aliens Speaking English in the comic, but this language difference is a plot point later on), you'd expect that the only use for such an anachronistic expression would be because of the translation convention.
Though it's never made explicit in the narrative, Word of God has it that Tales of MU is "translated" from Pax, the fictional language the narrator speaks.
More Tales Of MU also translates elvish into English, since that narrator is bilingual. The rotating viewpoint side stories tend to translate all dialogue into English, regardless of what language is actually being spoken.
Tales of the Questor is probably an example of this; the dialogue is in English, but the Rac Cona Daimh written language is depicted with a completely different set of symbols. (Which is created for the strip using a font called Lovecraft's Diary.)
Toki No Tanaka has all of its Japanese dialogue (ie. all of the dialogue) presented in English. Any background writing (signposts, etc.) is rendered in untranslated Japanese, however.
In Yokoka's Quest, each spoken language has its own speech bubble and font style and colour, to make them easily distinguishable. These are shown as illegible text if the perspective character doesn't understand it.
Exceptions
While And Shine Heaven Now mostly plays this trope straight, what French there is-mainly coming from the Frenchman Pip Bernadette- is left intact.
In thisThe Wretched Onesuses different text color to depict different languages. Japanese is in red, French in dark blue, and an unidentified third language is light blue.
Mixed
Stand Still, Stay Silent renders Icelandic, Norwegian, Swedish, Danish, Swedish and Finnish in English. In scenes where different languages are spoken, speech bubbles carry national flags to indicate which language is actually being spoken and hence what side of the Language Barrier everyone listening is on (when there is only one language, it's implied to be whichever one is shared by everyone involved). However, dialog has occasionally been rendered in both Swedish and Finnish in scenes that were strictly from the point of view of someone not speaking the language, and Finnish magic spells are always rendered in Finnish.
with a ninja speaking to an Irish village for about 3 panels before it's revealed nobody understands him because he's actually speaking Japanese.