I am having a problem that is already covered by someone else's question, but none of the existing answers work for me. I've asked my own question, but nobody's tried to answer it, and I don't have enough reputation to bounty it. I would like to be able to comment on an existing answer to the other question regarding the errors which are occurring when I try to use their proposed solution, but I can't do that either because, again, I don't have enough rep. I am really, really struggling to gain any reputation, because I don't have any questions that need answering, and I don't know enough to answer any of the unanswered questions. How do I get past this incredibly frustrating blockage?
There are several ways to get reputation, upvotes on questions and answers are just the most obvious ones. Others are listed in https://apple.stackexchange.com/help/whats-reputation. But you should now be past the limit regarding comments anyway.
As for your question about Xcode: I was tempted to close it as duplicate because as written there is no mention of the things you've tried and the results you got when doing so. So a useful course of action would be to edit the question to actually show what you did (reference the other question if necessary) and how this failed to solve the problem. This will make the question more easy to answer (or at least to help you).
This inability to answer is a problem only for people completely new to the Stack Exchange sites.
One work-around is to join a different site where you think you can quickly earn reputation with your questions or answers (even if you aren't especially interested in that site).
Once you have enough reputation (I think it's 200 totalled over all sites), whenever you join a new site you'll automatically start off with 100 points and can comment and chat right away.