Entirely unmoderated tags are not an option for lemmy as the moderation workload would be too much. Additionally users being able to type out tags themselves introduces splintering in the tag contents due to typos. A better solution is a curated list of tags users can attach to their posts
I vehemently disagree with the main idea behind this RFC. Just let users put arbitrary tags on their posts and other users can search for whatever tags they want. The rest of the fediverse has unmoderated hashtags and it works fine. I don’t see a good reason hashtags should require moderation. And typos can be corrected by editing the post.
Adding those restrictions just makes this feature more complex than it needs to be and reduces compatibility with the fediverse. Users of any fediverse software can create a post in a lemmy community and those posts may have arbitrary tags. Why should lemmy users have less capability on lemmy than external users?
Finally, hashtags could be a useful way to filter posts within a community if these restrictions are dropped. I posted this in the github thread, but imagine a general programming community. Posts could be tagged with a language, paradigm (OOP, functional, etc), or whatever else to allow users to browse subtopics within a community. Having to request moderators add a tag is an unnecessary extra step.