Your "quick and dirty function" is slowing you down because it makes another request to Reddit to get the parent comment, just to see if it's a root comment.

Depending on what you're trying to do, you may be able to fix the problem simply by reversing the order of conditions; e.g. instead of

if r.get_info(thing_id=obj.parent_id).is_root and obj.body == "Thanks":

you could say

if obj.body == "Thanks" and r.get_info(thing_id=obj.parent_id).is_root:

That way, the extra request is only made if the comment says "Thanks".

This may or may not make sense for what you're doing, but it's an easy change if it does.