UPDATE: I've noticed SE is trying to fix some of these issues, but the fixes create problems of their own. Since these have't been implemented yet, I've made a separate answer on that post to address those issues.
Reviewers are encouraged to leave comments for the post-author, but now they can also choose from a few options of canned feedback which will appear as a comment from the Community account.
Sounds neat, but when you think about it:
1. It allows any user with 500 reputation to comment as official Stack Exchange
First of all, Community appears as a moderator. A lot of users would delete their posts if a moderator didn't approve (can you honestly say that a moderator's comment doesn't hold more weight then a user with 500 reputation?). Worse, anyone who reads the description on the Community account sees that it is an official Stack Exchange account. They would think that it is Stack Exchange itself (or an employee sending it from the community account), and with good reason, unless they happened to read this post.
2. It's anonymous
Users who send this are not responsible for their comments. Say a user were to have a personal feud with a user, or with a specific tag (such as not liking a particular programming language). They could choose "Question is unclear" on every question that meets that criteria, with little fear of retribution.
3. Replies are broken
Users could be very confused by this. They make a post that has too much code, and someone who reviews it would send the appropriate comment. They try to ask how to shorten it, but don't get a response. This could encourage reviewers to not care as much about a comment, due to not having to reply or be responsible in any way for it.
4. Users without knowledge of the new review queue workflow could think it's an auto-comment
Since Community is a bot, it would be reasonable to assume a comment from Community would be based on an algorithm, not a human review.
5. You can upvote your own comment.
The strange thing is, you can't unupvote it.
What is the reason for having comments be from Community?