It's not so much that the policy has changed, it's that certain users have been aggressively flagging comments lately.
Some of the comments that were flagged on the linked question included:
It sounds fantastic!
I remember reading a short story online about this but I can't remember what it was called or where it was.
I wanna read this, identify please.
The help center's information on comments says:
Comments are not recommended for any of the following:
Compliments which do not add new information ("+1, great answer!"); instead, up-vote it and pay it forward;
Since those comments don't add any new information and were flagged, I deleted them in accordance with the help center's guidance on commenting.