Sadly, with the size of the community, giving warnings would just be too time consuming when the mods are already dealing with an almost constant days worth of reports and other things piling up. Also, not many people actually listen to warnings anyway, which would only add more to their work load.

Just remake the trade if it's as you say, there wouldn't be a reason to close that one and it's much easier than dealing with mods.

Closing your trade was your warning. Your trade didn't get closed just because you "forgot to edit" out your "c/o".
If you even don't understand why, I don't see how any other form of a less impacting warning would've helped to make you understand and keep you from doing what you did again.

both c/o's were in the trade, the users hid their posts while i was asleep lol

Except, that's not it. You know it can take more than a day for mods to respond to a report? Maybe you should ask yourself what your trade looked like then. Just because you remove a "c/o" when someone calls you out to provide proof, does not make it right / less fake / less trolling.

i dont think you're understanding the situation here

Because it's far far far (far X 10^∞) too time consuming. I'm not joking when I say the time it takes to review a mildly complex report is generally the time in which 2 or 3 more reports are made.

There's no real problem with having your trade closed anyway, just copy paste the notes, (removing offending material). Bookmarks really don't matter in most cases.