With all that out of the way, I don’t see very many companies lining up to license a far left-leaning dataset that had all non-echo chamber discussion banned.

Maybe this isn’t what you are saying, but Reddit (at least in the past, on smaller more expert subreddits) is no more an echo chamber than any other politically charged community space online, it’s just in other communities the rightwing people who control the levers of power usually don’t let leftists have any kind of voice or power in the first place.