Stack Exchange sites are founded on the principle of being distinct from the rest of the Internet by trying to do one thing, and do it well.
That one thing is to provide specific answers to specific on-topic questions.
Yet this site in particular tends to end up with individual users who repeatedly make the same sorts of off topic posts and either don't care, ignore, or make invalid arguments when it is explained that these posts are off-topic. Hence the pattern of inappropriate behavior continues unchecked.
To take some specific examples
Posing the same "trick" question over an over again on a topic where the poster somehow believes they have something novel to expound, but won't actually make their point until the community has wasted days guessing down their indirect approach to the matter. Despite repeated closures and explanations, this person just continues re-posting the same lead-in to their own future revelation. Whatever the technical merits or non-merits of their ultimate idea, what they are trying to do is blog - and EESE is not a blog.
Posting "answers" which are lengthy catalogs of personal experiences and tangential web searching only related to the actual question in the most distant ways. Occasionally there is a tidbit of something non-erroneous and actually relevant or possibly useful buried within but it's all but impossible to find in the literally pages and pages of tangential and often seriously erroneous blabber of this user's habitual posting style.
Posting conversational discussion forum responses which don't actually address the question, but only tangential things where the subject typically has much more to do with the poster's personal experiences and expertise, than with the actual question. And especially this habit, when the person goes and digs up ancient, well-settled or essentially off-topic-to-begin-with questions to post in response to.
I don't think the people who do these things really have nefarious intent - rather it's a matter of user education. So far they do not, can not, or will not take time to understand that Stack Exchange is something unique and distinct - that it is a QA site, not a discussion forum and not a personal blog.
So what do we do?