Sometimes you don't have anything to add to a colleague's comment, but you want to show them you agree or that you've read it. In this case, you can acknowledge a comment by adding a 'thumbs up'.

You will see a 'thumbs up' icon at the bottom right of every comment when you hover your cursor over it. Just click this to add your acknowledgment.

When you have added your acknowledgement, the thumbs up icon will appear in blue.

Multiple team members can add their acknowledgement to the same comment by clicking on a thumbs up icon that already exists. 

If you want to see who has acknowledged a comment, just hover your cursor over it the icon.

If you disagree with a comment, or have a scenario where you'd want to add something other than a 'thumbs up', we think that warrants an explanation. In this case, you should add a new comment.