I know some folks have used RSS for many things on user accounts as well. Sometimes there could be a reason you cant subscribe to a user or magazine and RSS is a way around that. I subscribe to my mastodon rss feed just for fun too.
using the RSS feed you could link it to a blog or personal website as well and share your posts in a way to others who may not be on the same site as you. Like sharing your posts on your websites so others can see on your site what it is you post so they dont have to have an account as well on kbin for example.
Or you can get a RSS firehose of accounts together to keep up on things outside of the community to ensure you dont miss something in your /m/sub feed.