I have seen lately, a lot of things that could be questionable considering the guidelines.
1) A vote log: This is something I myself have done, but I'm not sure if it falls inside of the category of vote soliciting. I would assume that it would if you're like "vote up to keep the log going!" but is it soliciting normally?
2) Asking to not spin off: I have also seen a lot of this recently, where it's like "please don't spin off or use this code without my permission". Unless I am mistaken, I believe that that is not allowed.
3) Asking not to vote up: I think that this is kind of a controversial topic, because asking not to vote up can either mean that a) They are trying to use reverse psychology to get votes, or b) They are trying not to get their programs voted up, typically because it's a work in progress and they'd rather have their programs be a "surprise".
4) Posting a link to a subscription page: Many people post a link to their subscription page in the Tips and Thanks of their project and be like "sub here, it would mean the world to me <3 [link]". I myself am also guilty of this, but I have wondered (for quite a while) if this is actually allowed.
5) Using "advertising" content in programs: I have seen projects that might "advertise" different non-khan websites. Take YouTube, for example. I have seen many versions of KhanTube. Or Cookie Clicker. Or MineKhan. Or mobile games recreated. Or older arcade games. Certainly this would be allowed, because if not then nearly half of the programs on the top list would break the guidelines.