It seems like this only supports mob mentality, where many other users will simply follow one because the first one said so. If a question was truly bad, users would flag it without the 'reminder comment'.
The comment is primarily there to provide feedback to the OP. Whether other agree with it or not is secondary.
Think of it from the OP's point of view. What would you rather see, a question closed with only one of the canned text to explain why, or a more detailed explanation from someone that voted to close?
Occasionally someone on the fence about whether a question should be closed may be swayed by someone else explaining their reasoning for closing it. There is nothing wrong with that. If that's happening, then the question is borderline at best. I'm just not going to get worked up about what happens to mediocre questions.
We also sometimes see the reverse happening. A close vote or two accumulates, and someone argues that the question shouldn't be closed for a particular reason. These arguments can sometimes be effective.
If you don't like that, don't post mediocre questions. Clearly that's possible, since most questions don't get any close votes. If we lose a few questions that are at the 21st percentile instead of the 20th percentile, it's no real loss. We get plenty of good questions. Doing anything but dispensing with borderline questions in the most expedient way is a waste of time and noises up the site. If the mob helps with that, OK.
If somebody voted to close a question, the system automatically generates indicators. The questions is added to the the close review queue. "close (n)", where n is the current number of close votes, appears on the questions itself. This is visible to those with close-voting privileges.
Why, one may wonder?
- Because everyone like a clean stack.
- Because a closed mediocre question is not a big loss.
Not for an O.P.
Not for the rest of us.
See also this.
It's not that its allowed -- its that when prompted for certain "other" close reasons in the close menus, you're forced to type something, and that something is automatically added to the comments. A person who is closing something that wants to provide an accurate reason has no choice as to whether to provide a comment or not.
In short, the close system, in certain cases, reeks. Often, I'll just check "unclear" because its faster. If SE wants me to provide real reasons, they'll take a close look at their close system and figure out how to change it to make it work better.