On blogs and Internet discussion forums, when participants use the SGML-style tags popularized by HTML (or sometimes BB Code-style tags) to accentuate their messages.
Sometimes these tags can include attributes such as <flame tone="angry">...</flame>.
Oftentimes the opening tag will be omitted and only the closing tag will be there, as a kind of self-conscious lampshade hung on the preceding flame/rant/etc. It is also used to show that a sarcastic rant mocking the opposite side of some debate is just that. Everyone KNOWS that first person is good wiki syntax, after all. </thattroper>
Can also be used in image macros. Note that not all edited photos are image macros: Some humorous pictures are seen on the 'Net, such as a man with "</head> <body>" tatooed on his neck or a tombstone with "</life>".
Anti-war candidate Darcy Burner wore a T-shirt with </WAR> on it in several photos.
Adam Savage frequently wears a T-shirt that states <mythbuster> "Am I missing an eyebrow?" </mythbuster>.
</unsubscribe> is occasionally used on Usenet to indicate that one is unsubscribing from a thread. However, the proper use should be either </subscribe> (to indicate that the subscription is ending) or <unsubscribe /> (XML empty tag to indicate an unsubscription). It probably means, though, that the person has just finished the process of unsubscribing. </justifyingedit>
This used to be done with faux C preprocessor directives, e.g.:
- #ifdef FLAME#endif
Also known as Ostensible Markup Language, although it's not the only meaning of that phrase.
The successor phenomena is #HashtagForLaughs