Regarding the second point: "What happens if someone with less than 3000 reputation leaves a comment that they wish to vote to reopen?"

Obviously leaving a comment has no effect, but to this point, would it be worth having a mechanism for reputation-deprived users to call attention to particular questions/answers so that other users with more reputation can take a look and decide whether to reopen or not?

This could also apply to other features that also require reputation, not just reopening a question. What I'm thinking of would not be intrusive (i.e. it would not send out messages or anything).

For example, I'm thinking that there could just be a list of questions that other users have requested be reopened, sorted descending by the number of users (or better yet, the sum of the reputation of those users) requesting that it be reopened. If any users who have enough reputation to reopen want to peruse that list, then they can do so. If not, then they don't have to.

Basically, I'm suggesting a mechanism that allows users with low reputation to still have some kind of input towards causing something to change, even though it requires the intervention of another user who has enough reputation to enact that change. The benefit is that you're not leaving it up to chance that enough users with high enough reputation have happened to stop by on a particular question, noticed the situation, and decided to take action.