I've seen a few posts in the past couple days, mostly from new Community users, who are finding old posts from 2015 and 2016 and replying to them with "tweaked" versions of the problems solved in these posts. This is tough for a few reasons:
1) The people on that thread may not frequent the community today, so the question might not get visibility
2) The new poster can't mark any suggestions as a solution
3) This causes notifications to active users from old threads, which may not be appropriate if their issue was already solved.
I think if there was a date after which threads were locked that would help. To enable ease of use for new users, I think adding a new button "Create Related Thread" to these posts would help new users to post their question quickly.
Clicking this button might inherit the Tags that the old question had, and write the header for the user, and maybe include a link to the old thread for context?
I think this would help a lot with the experience of new users on the Community, and would also give more visibility to these kinds of "modified" requests.