How to report a steamtrades comment?

You don't,
That site has no mods...

All i can do i say sorry for the stupidity of some people.
try barter vg or lestrades for less "comments" and more offers

There is no moderation on Steamtrades.

you can't , ST is a wild land, move on

report for a political comment?

Guidelines

User Content

The below is a list of content that is not allowed in our community. Content consists of any material you post or make available through our site, such as discussions, links, comments, usernames, or Steam avatars.

13.Trading. This site is not for trading, so do not attempt to directly trade games or other items with users in our community. If you attempt to indirectly trade or express a willingness to trade with an unusually high frequency, it will also be viewed as trading.

The developers(CG) of Steam Gifts and Steam Trade are the same.
But it's a completely different site, and bringing in the topic could violate the above rules.

From time to time, it seems that there are human beings who try to bring in relationships (slandering) in Steam Trade.
However, it seems to be an act that conflicts with the above Guideline.
And I have never seen them again.( 'Θ`)

As others noted - there is no moderation section on ST. So support staff that is on SG can't do anything about ST.

Those two were separated ages ago, and now only form of moderation on ST is voting done by the users on reputation. Democracy wins? :blobevil: