@skuwamoto @futurebird It's an issue of governance; in general most instances have more or less the same rules, but the expected behavior of people is practically the same: Don't be racist, don't be a bigot, don't be an asshole.
Different servers have different rules because that's the nature of decentralization in a microblogging platform. It's not perfect, but it's something.
Regarding hashtags, well, I can't say they're equivalent to a subreddit. If you like to talk about a certain topic, then sure, but I'd say you can use hashtags to find people with similar interests to follow.
So yeah, you're right: There is indeed a discrepancy between your network and the hashtags you follow. The ideal would be to use something like groups or circles, but circles haven't been implemented yet on Mastodon, and to create a group you need to set up an account in some special server whose name I forgot. In short, it's complicated.
BTW, if you want something more similar to reddit, you can search for lemmy servers, where each server has its own set of rules and its own communities.
(example)