This question keeps on coming again and again (even today).
In most cases when a forum member deletes his own posts from a thread (or threads) in anger or otherwise, it leaves the rest of the thread somewhat incomprehensible or at least with some disconnects. Some of the follow-up posts by others may become irrelevant if these follow-up posts were comments on info in the deleted posts. So it does make not-so-good difference to others on the forum.
Also, in cases where someone had asked a genuine question on the forum and if someone properly answered that question then most probably other members may cease to repeat answering the same question to avoid repetition because it already got properly answered. Then if the one who had first answered the question decides to delete his answer, the thread is left incomplete.
However, if we want "Edit" function then "delete" come as a consequence of the "Edit" availability.
I had asked about it and was told that everyone is free to do with their posts whatever they wish. However, leaving the option of 'deleting or not deleting in anger or otherwise' to the judgment of the poster may not always work to the benefit of the forum and its members such as in cases of extreme anger. Deleting own posts cause issues for other members and damages the information repository and may need some reconsideration.
The one solution, if feasible, is to allow "Edit" within a fixed known period after posting such as one week period and then auto-lock the post. Any edit, if required by the poster, afterward can be done through a new post.