Strange idea, i doubt it will set foot, but just spreading my thoughts

Hello there,
A bit strange indeed, considering a lively lobby is something that many love to see in a game like diablo2 as it brings a lot of nostalgia and interaction. Almost everyone who posts their own message usually gives it a decent time in between the next trade message though (at least a few minutes in general) so that's not really spamming. Here is a good example of spam https://imgur.com/a/M7Lp1Za where battlenet spam bots used to and still flood the lobby channels to this day which obviously does not happen here at all. Also, if someone reposts their message too fast then they will always get a reminder either from the other players or from moderators via whisper but that happens occasionally as most people do follow the channel rules otherwise they could get a temporary mute for flooding.
Regarding your idea, think of this simple example: why do you think popular websites like ebay or craigslist (or pretty much any similar website) have mostly selling ads and not buying ads? It is because people, in general, will prefer more to have something to choose from rather than post what they're interested in themselves. You can see the same thing here and pretty much everywhere else too.
And what about the times when people share their thoughts and discuss either a build or strategies at a fast pace and there's quite a lot of text going on? Spamming is a bit different and depends on the situation as well. Considering the ladder reset is fairly recent, it's only normal for more people to be active in the channel and post their messages but fear not as we'll take measures if it becomes too spammy.