I'm both surprised that people react so strongly and... mostly ok with it. Majority of GDPR is pretty reasonable - know what data you have and make sure your users know it as well. Allow removing it, make sure you don't share with parties who don't need it. For normal services it doesn't appear to be a tough retirement.
You certainly don't need to hire extra people like author suggests and federation should be just fine. (it's essential to what the service does)
We're talking about chat.. you shouldn't be logging the contents, at most a bit of metadata to prevent abuse (eg. a connection log to identify and block spammers).
If you don't store that metadata longer than needed (a couple of weeks? storing it for years would be hard to defend) you have legitimate reasons to keep it, and don't need to worry about deletion requests
That's why I mentioned I'm ok with projects reacting strongly and removing themselves. Removing my info (and many other GDPR points) is in my interest. If they can't do this, I'm glad I won't be their immortal user.
I was going to say the same thing. If you're an individual running an OSS service, or a small business, requests for information or deleting information really are going to be really rare.
You certainly don't need to hire extra people like author suggests and federation should be just fine. (it's essential to what the service does)