Counting @mentions in the limit also 'punishes' people with longer names.

But I guess if you didn't count @mentions in the limit you'd find people adding lots of people to a conversation in a spammy way. I'm not really sure how to fix that.

Perhaps there could be a meta-@mention that would include all previous recipients in a given conversation. But then how do you remove people from a conversation? Arggggh!

(Still, i've only thought about this for 2 minutes. I'm sure there's a way that makes sense if you spent more than 10 minutes working it through.)