The number of subscribers listed in the sidebar is only the number of users from YOUR instance that are subscribed. This might make you feel like a community is 'small' or 'dead' when it actually isn't.
I also started to forget this till I was playing with the shields.io badges earlier and the numbers didn't match up.
This is such a useful post.
As a lemmy newbie, I see that there is a save functionality, but is there a way to tag posts like these so I can reference them in the future?
Do you mean so that you can search for it in your saved posts more easily? If so I don't know of any tools for that yet. I've been saving things to Pocket when I want something like that.
Back when I was using Reddit, I set up IFTTT to add my saved posts to a spreedsheet on my google drive. It stopped working a few months ago and I never fixed it. You could try something like that, but it might be easier to just save it with some other service (bookmarks or Pocket type services)