Plus-addressing is built in to most email services. There's no 'fancy' set up to break; it just works. That is, there's no way [email protected] works but [email protected] doesn't, unless you explicitly configure it not to work. Similarly for custom domains on most services.

If you use a catch-all on a domain, i.e. [email protected], I guess in theory that might break. But it seems about as likely as messing up the overall domain setup.

Also, my account on your service is likely much more disposable to me than my email address/domain. Anything I care about, I'd back up. Not just assume some random website is going to preserve it for me forever.