These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: Dumbing of Age
Base Breaker: The whole Billie vs Ruth thing has people picking sides.
Also is Joyce an adorable Christian who needs to break out of the effects of her sheltered life or an idiotic bible-thumping xenophobe?
The storyline involving Sal and Walky's parents preferring Walky based on racial preferences created a massive outpouring of both complaints and support from fans.
Dina won the "favorite character" poll, despite having less than 40 strip appearances by the time the poll closed. For comparison, Walky had over 150, and Joyce over 250. The poll currently had her at 603 votes, 19% of the total amount. The second highest was Mike and he only has 482. That means nearly a fifth of the fan base loves her more than the main characters. She's featured in the banner ads for the comic, where she's hiding just out of frame (so just her Cool Hat is visible), pops up to stare at the reader for a few seconds, goes "Rarr!" and pops back down.
She's since won for a second year running, this time with a whopping 43% of the vote.
Leslie. Despite her limited appearances, she generally liked by the fans for being a Cool Teacher and having a great sense of humor.
Escapist Character: The author says Dorothy is at least partially one for him. Certainly, she is quite successful and ambitious, with quite possibly the only good parents we see during Freshman Family Weekeend.
Author Comment: [All my characters] take things from me on some level. [...] Some day, I hope I will be Dorothy. That is my end game. But I still have lots of stuff to work out first.
Harsher in Hindsight: Walky's casual joke about Sal being blacker than him REALLY comes back to bite him.
With my penis tends to pop up in the comments of most strips involving Joe. It eventually become the response to any action, regardless of if Joe is in any way involved. Usually immediately followed by Mike's catchphrase "For a nickel."
The Show Within a Show "Dexter and Monkey Master" is often treatedas if it were an actual show◊. Creating the most bizarre meta-fandom, as the show's "fans" argue about which episodes are the best, wishing the series had continued, even criticising Walky's and Leslie's lack of taste in episodes. Comics featuring D&MM will typically have a long comment chain featuring the input of an irascible and argumentative fandom for a show that DOES NOT EVEN EXIST. This mentality has even carried over to Joyce's favourite Christian cartoon, Hymmel the Hymnal!◊
Sarah also got a lot more sympathy from the base once her full circumstances were revealed. She didn't call the cops or the school on her roommate, she called said roommate's father, and he pulled her out of school.
Ruth is disliked by a lot of fans for her rampant abuses of power and haughtiness.
Danny's behavior when it comes to relationships really rubs a lot of fans the wrong way. Not just that, but a lot fans admit that they dislike him because he reminds them of themselves at some point in their lives. Additionally, numerous fans accuse him of being facetious Nice Guy (being Neutral rather than Good) and having some of his decisions motivated by an It's All About Me attitude.
The vast majority of the parents revealed in the Fall Family Weekend arc, for their awful treatment of their kids. In particular, the Walkertons and the Siegals got hate almost immediately after being revealed for their treatment of their kids, and while the Wilcoxes take a similar view of Danny as some comments, it's a lot more uncomfortable when being said by a parent to their child. And while the Browns started off with some optimism, their pressuring Joyce to stop being friends with Dorothy made them drop rapidly in regard. There were a lot of comments guessing how any of them could be only the second-worst parents in the arc (particularly the Browns and Siegals), right up until the reveal of Blaine O'Malley, every bit as abusive and awful as he was in Shortpacked!.
Danny is being castigated for worrying that Billie might later regret having sex with him. He doesn't defend himself by pointing out that Billie said she might later regret having sex with him.
For all the people talking about Billie's sexual choices not being respected (in the comments and on tumblr), very few of them seem to have realized that the strip is shaming Danny's sexual choices in a way that they certainly wouldn't if the genders were reversed. He even says he doesn't want to sleep with strangers who throw themselves at him, and as clearly uncertain about having casual sex with her after just flirting, then her taking offense, then him apologizing, then deciding to "casual-bang" him.
Billie herself doesn't seem too distraught about being turned down.
Walky not believing Sal's accusations of parental favouritism due to racism is supposed to be part of his childishness, but it is understandable that he would be offended on his parents' behalf and Sal does tend to blame others for any of her faults.