This argument seems to be based on preventing users from trying to get easy badges (targeting the robo-reviewers) rather than making reviewing better. You have to accept that as long as there is an award, there are some people who are going to take the path of least resistance to get that badge. We will always have robo-reviewers, you can't stop or prevent it, so all you can do is help limit it without impacting the ability of reviewers from doing their job.
I don't think this should be so because this will be an alternative for users who don't concentrate on the post. They'll just upvote a comment and click "I'm done"
Good, I'd rather them do this than something else destructive. It is just as easy to upvote or downvote a post as it is to upvote a comment, so if robo-reviewers are not just clicking "No Action Needed", then I'd rather give them a non-destructive action to perform. By reducing the options for robo-reviewers, you are going to encourage them to vote on posts and that is harmful to the site. In fact unnecessary voting on posts is the main reason "No Action Needed" was added to give robo-reviewers a less harmful action to perform.
This should be disabled or comments shouldn't be shown on reviews.
(Emphasis mine). Why in the world would this be helpful? A couple of months ago, commenting on reviews was broken and there was a major uproar about it. Comments tell you a lot about what has already happened and helps your review better, and also avoid duplication. A what would you rather see a single comment with several upvotes or duplicate comments that effectively say the same thing? This was the whole reason this was added.
So will this prevent robo-reviewers from voting on comments just to get past the review quickly? Yes, it will, but they will find another way to review quickly and that way may be more actively harmful to the site.
So looking at regular reviewers and not "robo-reviewers", you are now going to encourage them to vote more. And typically, it is going to be on poor quality posts, which means a downvote. Not everyone wants to downvote a fixable post right away, especially one that has a few downvotes already. Many will hold off on voting to give the author a chance to address what is wrong.
Imagine a hypothetical post from a new user that is only missing 1 or 2 small bits of clarification. And someone has already asked in a comment about the missing info. Personally, if the post could be good, I don't think voting at that time is right. I'd rather give the user a chance to fix it, especially if they are new. Too many quick downvotes are just going to discourage them and possibly prevent them from returning to address the comment. So if I am not going to vote yet, what are my options?
- Leave another comment saying the exact same thing as an existing comment? We don't want that, in fact, that is the reason this was done in the first place.
- Upvote the comment to show support for it?
In the end, the comment upvote is helpful for regular reviewers and helps limit noise on posts. And just like too many downvotes can be seen as piling on, too many duplicate comments can have the same effect to a new users, so the ability to upvote helps limit that. Sure, you can still do that, but in order to get out of the review (and get credit for it) after upvoting a comment, you now need to do something else, and that's the problem I see.