I think there's a few things that people need to consider when creating rules for themselves or communities, and with setting boundaries for yourself or a community.
Is this boundary or rule something I can actually enforce?
A really wonderful way I saw this phrased a while back was like this: you can't actually set a boundary that is phrased like "don't cross this boundary". Because someone will - and now what?
Instead, phrase it with action: "If you cross this boundary, X will happen to you".
Now here's where the "actually enforceable" part comes in. Can you actually follow through? If the boundary is "If you're a terf and you follow me, I'm blocking you", that is an enforceable boundary. "TERFs DNI" is NOT enforceable: you cannot stop the initial interaction, this is a public website! You can block after the fact, but you cannot force them to not interact in the first place.
2. With regards to more interpersonal relationships and communities: is the boundary reasonable, and is the consequence reasonable?
Will setting this boundary cause more harm than good? Will it make communication in your community difficult?
I saw a great boundary set in a trans reddit the other day: when regarding the outcomes of a surgery, you cannot use the word "results". You can say "great chest!" but not "great results!". The consequence for using the word "results" is that an automatic bot will simply delete your reply and respond with the message "Using the word "results" is not allowed on this subreddit".
This is a clear boundary: do not use the word "results". It has a clear consequence that is easy to enforce through the use of a bot, and the consequence isn't public shaming or anything cruel; your reply is just gone, and you can then rephrase yourself. The boundary is clear and the consequence isn't disruptive or harmful.
Also, it's one rule. That's easy to remember.
BUT this isn't the case in all communities. I've tried to join many a discord server with an endless list of blacklisted words and phrases. The consequences for using these words are always harsh, and public shaming for daring to violate the boundary is extreme. I personally don't stay in communities like that; I HATE walking on eggshells, worried at any moment I could inadvertently say something from the long list I can't possibly memorize, and suddenly I'm a horrible villain.
So. Keep your boundaries and rules reasonable and enforceable, and make the consequences logical and not cruel.