This rule is implemented so nobody goes downvoting every answer they don't like. If you lose reputation for down-voting, you will think about it before casting it. This was also put in place so users don't abuse the system by down-voting excessively and indiscriminately.
From this answer on main meta:
According to what Jeff/Joel discussed on the SO ...
The earlier answer by @AJ is fundamentally correct in saying that
this rule is implemented so nobody goes downvoting every answer they don't like. If you lose reputation for down-voting, you will think about it before casting it.
May I only add from personal experience that a nominal -1 loss of reputation for casting a downvote or -2 for getting a downvote ...
The simplest answer is that if you see an answer with delete votes and no comment, then add a comment. If you cast a delete vote, add a comment.
I figured that, since I was the first one to vote, someone else would leave a comment afterward.
Not necessarily. The only thing that you can control on the stack is the actions that you take. There are several ...
How to avoid answers being deleted without a comment?
You can't really stop a post with no comment getting deleted. It is us who have to make sure that OP knows why their post was deleted. However, OP will always see a link to this page whenever their answer is deleted, but this link is not that helpful in case of IPS.
So, what should you do?
If you're ...
According to this post six recommend deletion votes will only automatically delete a post if it has a score of zero or less. So, if it was at 1 when you submitted your review, it wouldn't be deleted.
Yes, a sufficient number of delete recommendations (currently 6 on most sites, 4 on Stack Overflow) will cause the post to be deleted immediately, provided ...
What actually happens to the answers that I recommend deleting?
When it gets six Recommend Deletion clicks, this answer will be deleted and will be shown as
Deleted from review by [users' names who voted to Recommend Deletion] [date of deletion] at [time of deletion]
See this item for above scenario,
Remember, this button text is changed for users with ...