I posted a question on Stack Overflow: Postgres: Why did adding index slow down regexp queries?
Because of lack of reactions, I later posted the same question on DBA Stack Exchange: Postgres: why did this trigram index slow down regexp queries?
It got answered on DBA, and I accepted the answer there.
Problem: Now I cannot delete my SO question, because "others have already invested time and effort" (there's one answer already, though not terribly relevant).
I cannot close it as a duplicate either, because that would require a link within SO (not to DBA).
I cannot provide and accept the correct answer either: I tried posting an answer on SO linking to DBA with a short explanation, so I could accept that. But no luck either, I'm getting some "your answer was trivial so we automatically converted it to a comment" nonsense.
Any other ideas how to close the question, providing the correct answer?