These days just about any popular thread that I wander into, I see wide swaths of "deleted" comments. I'm sure they were deleted for many good and valid reasons.
IMHO, reddit's aggressive moderation suppresses spontaneous comments and is off putting to lurkers. The wittiest comments are likely spontaneous. And lurkers are not likely to engage in a discussion if they feel it may be off topic.
So we miss out on spontaneous humor and the random insights of brilliant people.
All of this makes reddit a sadder experience.