@stevebaer i would like to point out that this function seems probably a bit misleading for some. i had now 2 cases where somebody clicking through several posts probably believing that they all will be marked as such. from one topic i had this even flickering up on every post i made.
maybe some sort of feedback that they know that only one solution will be indicated, that one which they believe helped them and will help others solve this issue the most, something like a warning when the solution was already checked when clicking the 2nd time.
maybe thats a misunderstanding anyway, but having this happen coincidentally twice in a short period gave me doubts about it being clear for everybody.