I am not sure whether I should write this on MSE or MAU, but here I go anyway
Context: Couple of months ago, I came across a dearly interesting question related to corrupted desktop environments (unfortunately, one of these). The question was answered fairly well by a user "X" who had about 500 reputation (the answer wasn't accepted and had only one or two upvotes, but was factually right and well formatted).
Lately, I happened upon the same post and noticed that, that answer had been deleted by the user. Upon further investigation, I discovered that a different question with an identical body to the former question has been posted by them and self-answered with the exact same answer and have got a reasonable amount of upvotes on the question as well as the answer.
I could be wrong with my assumption, but the main objective is to know what stops a user from doing what is aforementioned OR if it is allowed/encouraged to do the same on SE.