I did this one time and my account ended up in a broken state where friends couldn't send me messages in long-running one-on-one Messenger chats (they got some mystery error like "This user is not accepting messages right now."). Group chats still worked and I could send messages to those same long-running Messenger conversations.

Re-activating the Facebook side of the account resolved the issue. Caveat deactivator.

You can indeed! You can even reactivate your account _only_ for messenger.

I kinda wish you could do that for events...

Yep. It currently explicitly states this and does it by default when you get to the final deactivation step. Previously it was an option you had to notice and click.