If you see self-vandalism, i.e. a user removing the substance of their question and replacing it with garbage, then please:
- Flag it (and explain what's going on in your flag; “self vandalism” is enough);
- Revert the vandalism, but only once (if this gets into an edit war, let moderators deal with it). (Exception: if the question is replaced by grossly offensive material, it may be warranted to edit again.)
If you unvandalize a post, please leave a polite comment requesting not to do this. What to say in the comment depends on several factors:
- For an unanswered question from an unregistered user (it says “unregistered” on their profile page), suggest that they can click the “flag” button underneath the question and request deletion.
- For an unanswered question from a registered user (it doesn't say “unregistered” on their profile page), suggest that they can delete the question by clicking the “delete” button underneath the question.
- For an answered question, explain that we don't delete answered questions, because that would take the answers away as well.
The same goes for highly-upvoted answers. For answers that weren't really worth keeping in the first place, just getting the answer to be deleted through normal means (e.g. the low quality queue) is enough.
By the way, many cases of vandalism (including this one are caught by a bot whose main job is to detect spam. This explains why you might see edits to revert vandalism from people who don't normally use the site.