What should you do if an experienced trader is acting weird?

Okay, so the situation is this. My friend got added by a relatively experienced trader using a known alt, and he asked to buy his unusual. My friend asked for what his offer was, and he said he doesn't know, because he was new. Obviously, this was a lie, but it checks out if you didn't know that the trader had this new alt. Anyways, my friend acts dumb, and then says he doesn't know the price either, which, for some reason, causes the alt to stress again that he is new, and then immediately block my friend.

So what should he do? Should he report him for suspicious behavior, or should he just let it go?

Well, it depends. I presume that said trader was hoping that your friend would sell him the unusual for a very cheap price. As far as I can see, this was an attempt at sharking, but Steamrep does not mark for sharking. However, deceptive activity is judged on a case by case basis. I would advise, if your friend has images of the chatlog to use his own judgement. I doubt a report will result in a scammer tag since no scam actually took place, nor was one attempted (again, sharking ≠ scamming.) However, the worst that could happen would be that the report would be archived.

I personally, although I highly dislike this type of behavior, would not report it, your friend however can do as he wishes. If he feels that said person was being deceptive or malicious, then it may result in a caution tag. I'm not an admin so I can't give a complete idea, but in most cases I've seen, sharks are not tagged.

Hope this helps.

Any advice helps, thank you.