What is the "Trade" channel in D2R and how does it work?

So uhh, I see when I create games and play every once in a while I auto-join or auto-leave the "Trade" and "Game" channel. I was doing some Summoner runs for Hate Keys when this happened out of nowhere
I don't recall if we're bnet friends from a trade or something as their in-game names don't show bnet tags. They were not in my game at the time and didn't reply when I said something back in the trade chat channel. Just to make sure, I ran around the area where I was farming and in the towns of every act to see if there was something on the Ground and I just missed them popping in and out of my game, but I saw nothing. I don't have currently have an agreed trade through here or another site, so this just left me really confused. They're also not random ghost messages from a random previous playing session I think as I don't trade by dropping stuff on the Ground, unless it's a gift or something extra.
Looking at my "all" from previous play time just shows I joined and left the game and trade channel every time I start and stop a run, I also don't see prior whispers so I have no idea where the conversation from that trade channel popped up from. In the settings I also don't see an option to just never join the "Trade" channel as I have no clue what it's for currently and how it works. Apparently people can talk and it looks like they're in my game, but then I don't see anyone nor does the message seem to be meant for me.

Bit of a ramble this post, but that's because this just really confused me and I wanted to make sure that someone didn't randomly come in and drop a gift that I then ignored. It's just a private game, not one created in lobby, but I do have it turned on that friends can join directly. I also don't see any message that someone joined my game and left in that session, so it just seems really weird that I can receive such a message while alone in a game doing some runs

Yeah, I really hate the in-game chat system in D2R. It is really clunky, it's hard to use, and it does random shit like this. I don't know why this happens, but every now and then it puts you into a trade channel and then you get weird messages on your screen like this. I really hope they rip this system out and re-do it in a future patch.

Ah, glad to hear it's not just me at least then! The chat functionality does seem quite broken in its current state. Even in the little snippet you can see that every message about leaving a channel pops up twice and you have absolutely no control over how you join or leave channels right now. I wish I could just permanently disable the trade channel all together as it's just clutter anyways and pretty much all trading is set up outside of D2R or by creating/joining specific game names

It's been a long time since I've played the old D2 on bnet, but aside from being a bit rudimentary, the chat worked well back then I think, right?

it seems to be filled with creatures who want to communicate. But alas, intelligent life has yet to be found