I'm sorry to hear about your experiences. I find it hard enough to deal with pushy people who have mismatched expectations (and yes, I'm not proud of it but at times I have been an entitled user.) I don't think what you're describing is limited to open source software though. Any time you make yourself available to the general population you're going to attract the full spectrum of human behavior. I guess the trick is to not make your project a honeypot for the debilitating stuff.

> I've learned to draw much stricter boundaries.

Could you elaborate on what has worked for you?

I imagine people who work in customer service have strategies too.