Unless anyone knows another reason for this impressive increase in comments? Seems to roughly coincide with Sync launching. If thats the case, just goes to show the importance of good third party apps.
Source: https://lemmy.fediverse.observer/dailystats
EDIT: Looks like a confusingly labeled graph and I think this is total comments. I have no idea why that spike could exist though.
It's confusing. It's "average per day" because the number fluctuates based on uptime for various instances.
There are also instances which have completely shut down. That, and comment purges, as you mention, can cause the number to go down. It's also somewhat possible that defederation between one site or another could cause it to fall off the stat sites' trackers.
But the main point stands. The comment count jumped up BEFORE SYNC EXISTED.