Honestly, I think that depends on the customer and their reaction. I might be slightly surprised but I go by a nickname to most people so I wouldn’t think too much about it.
I’d be more concerned that there are processes to keep the communication secure and good ways to verify that it’s Monzo who are sending it. In this case, I think that’s working well although there’s always ways to improve that.
99% of people wouldn’t care enough to check it out or even know what it meant so they’d just crack on.
Don’t overthink it.
I bet he pretended he was called Carl.
I can’t share 
Next you’ll be telling me @AlanDoe isn’t his real name! 
Can neither confirm nor deny.
Yeah, I remember when this policy was put in place. It was due to a serious potential security issue. Not just the adding on LinkedIn, which would be enough for such a policy on it’s own, but there was a time when disgruntled customers would show up at the office - and sometimes community events too.
If anyone here was at the final “Future of Monzo” event I hosted at Shoreditch Town Hall, you may remember me telling a story involving me and Eileen from Passion Capital (who gave the closing talk along with Tom Blom)
There were two reasons I did that. One because it was a fun story I’d always wanted to share. And the second reason was that I’d been asked to stall for time while a security issue was getting dealt with 
My AKA would be Tarquin Fin-tim-lin-bin-whin-bim-lim-bus-stop-F’tang-F’tang-Olé-Biscuitbarrel
(credit Monty Python).