I don't understand the part about awkwardness with customer service people. How often does that really come up? And, if it is predictable, just spend a minute

I don't understand the part about awkwardness with customer service people. How often does that really come up? And, if it is predictable, just spend a minute and think of some satisfying reply and then use that whenever it does come up. "Oh, hilton@notcheckmark.com? You must be a big fan." "Yep, cause of the great customer service." Done. Regarding shooting yourself in the foot by using nonstandard naming - seems an easy solution is to just use the entire SLD. If registering in person, I guess that's a bit harder, but either way make sure you save the login in your password manager.