Bad idea – the forum is a public resource, having users delete their topics after finding a solution goes against that goal.
That is what the solution button is for
Self-solutions aren’t really a problem. I’ve needed them too for some posts in #forum-feedback where I request a change, it gets implemented, but the people behind it don’t reply, so once I notice it myslef i reply to it, and mark as solution since it’s solved. I think you can report someone if they do it maliciously, since it goes against global rule 8.3