Alt-account confirmed, just read this linked review from MyIndieWishlist, another person attacked by this guy.
I have seen several bad reviews (without valid reasons) from this person these last days, I prefer to warn people who will try to trade with him. It's a user who -REP people without even having contacted them, make an offer or trade with them.
Here is my answer to the -REP he posted on my account.
This user joined SteamTrades today and posted this review only 1 hour after creating his account.
I didn't conclude any trade an haven't received any message and/or offer from him.
Apparently he doesn't know guidelines of ST.
[...]
As you can see his Steam account is private an he has no reputation.
I have always been respectful in my responses to other traders and tried my best to find solutions before declining if that was possible. And please, for your next review, watch your language, no need to be insulting ...