What you want sounds within Reddit's normal use case. If it's not a site feature, it's a feature of automod: https://www.reddit.com/r/AutoModerator/

There's a lot of subreddits configured to only allow text posts, one of the subreddits I frequent is configired to delete your post if it is an image post that doesn't have a top level comment by the poster, as the subreddit rules require all image posts to have text descriptions (to guide conversation/mitigate low quality posts).

I don't Tumblr so I don't know the full use case for tags, but from what you've described it sounds like flair: https://mods.reddithelp.com/hc/en-us/articles/360010513191-P...