From the comments in https://codeforces.com/blog/entry/67683, some questions, especially the last question in div3 contests are obviously overestimated, say 1176F. Also the difficultly for old problem sets may not fit current situation. Therefore is it possible to have a system allowing users to "recommend" the true difficulty of a problem, instead of using the current ELO rating system to esitmate (Ref)
A user is allowed in the system if he is experienced with CF, say participated in 10+ contests, solving 100+ problems, and having max rating>1900
User can vote on a particular problem if they do not join the contest and they solved it. For user participated in the contest, (1) their performance during contest has been considered in the estimated rating, and (2) they may read hints and tutorials after the contest and think the question is not difficult
User can vote on significantly over-estimated (should be at least 200 lower) / under-estimated / close to expected difficulty shown. If there is a strong tendency, update the estimated rating by a little step (50/100). Then the statistics will be cleared and people who never vote on this question can vote. Updates can be applied many times. For better visualization we may apply 50-interval instead of 100.
How do you think on the improving the estimated difficulty?