I’m getting annoyed with people that ask a question, have the community answer their question and troubleshoot over several days, only to delete their post and the solution.
The person asking the question is often providing the least amount of effort, so why should they have exclusive right to delete the contributions of others?
Possible fix: have a per-community option to only request deletion.
I think you can ban a community as a stop-gap? Wait for things to die down.
You can also edit to [SOLVED] which might deter enthusiastic helpers.