If you are the owner of a file, you will receive email notifications for all comments by default. If you are not the file owner and leave two or more comments on a file, you’ll be notified about all new comments that file receives.

I find it a little bit strange that if I tag some people in the file for a quick question afterwards when I leave comments to myself they all start by default to get notified about all the activity to the file. I understand the reasoning of making sure they are involved in the design process but I was using the function to keep track of some internal thoughts AND design feedback from the team that do not need to be shared with the rest yet. I was not aware about this default I just realised that there were people in the file after I made some comments a couple of times without tagging anyone.