If you are a seller you will also be looking for products to buy from other sellers to flip for profit, If you are a buyer, you are also going to be looking at all the other sellers offers. You can't do this EFFECTIVELY while switching between UNNECESSARY AND CUMBERSOME windows or tabs.
I do not like the whole merged trade chat HOWEVER I am VERY VERY VERY against splitting Buying and Selling into their own separate tabs.
/not signing
Please stop making your own threads for this- try contributing to the existing topics. And remember that your voice is one among many, no matter how many times you bump or quote yourself for emphasis.
(Remember that reputation is important. Based on how you conduct yourself here, I would NOT want to do business with you in game)
There is nothing in a split channel system that would prevent you from subscribing to both channels if you want to. It would give more control to those who want it, and in the absence of separate chat tabs, it would not penalize those who wanted more advanced functionality.