As a PR reviewer, I often have to leave comments in the pull requests. Examples of some of these comments might be:

• This line of code introduces a bug and needs fixing.
• This documentation wording could use some improvement.
• Would you consider making this text bold instead of monospace?
• This works, but I'm strongly in favour of using solution X instead as it I think it would be more maintainable.
• I don't quite understand your reasoning for this approach. Could you explain why you did this?
• This is really good. We should probably raise this in the next meeting to try and make sure we use this more often.

As you can see, the intent and the actions required for each comment are very different. Currently there is no way for myself or the PR author to rate or prioritise these comments, which makes it harder for the PR author to work out which comments to deal with first (if at all). 

Being able to rate/prioritise/categorise comments would help with this, as well as potentially provide a greater understanding of the intent of the person leaving the comment.

Possible examples of categorisation:

• Question
• Bug
• Potential improvement
• Required change/improvement
• General Feedback
• Info

If using a rating system, then something like:

• Blocking change required
• Strongly suggested change
• Possible change
• Question
• Info

A number system from 1-10 could potentially be used, though I feel it wouldn't do as much to provide the same level of context.

I'm not suggesting that all 3 types of rating are required, but at least one of them would be useful.