We'd need an objective way to measure lameness and then review a large set of posts (on a particular sub?) from a couple of months ago vs now. Criteria have to be pre-determined to avoid the post hoc fallacy.
Average words or characters per comment? Number of insults directed at other commenters (measured by someone blinded to which group they came from)? Number of "controversial" comments judged by large numbers of up and downvoted?
I dunno. I'm not doing it. Not a social scientist. Just suggesting an interesting experiment.
Skrewzem