Re: I guess NOFORN doesn't apply anymore?
A nick is not 100% reliable.
As you say, profiles get built, and at any point they might be able to link it with you, even after deleting the account. I still post most things in my name, even those that some ppl might find liebellous.
As for the whole anti-virus thing, I can only guess that it is mostly more embargo under pretenses.
I do think that having sw that always runs in your computer and is reading your files in computers that have secret data is a BAD idea, unless it is you who controls said software. So why run US based SW when it is as likely to spy on you as russian SW?