Always use the name "Shnell" whenever I play. It's a nickname, of course, but I've used it for awhile on other things that I feel pretty attached to it.
Don't worry about it, there is no way for him to physically harm your town in any way, without you two exchanging friend codes and inviting them to your island. :)
I think it might be only visible on your end, the deleted messages don't show up for me on your profile at all. Not sure if that helps, just letting you know
TBT is the forum currency, you earn it by posting and can use it to buy collectables/add-ons in the shop! IGB refers to in-game bells. Otherwise, welcome to the forum!