The post raises a valid concern. Some users have the habit of complaining rudely about unidentified other users, e.g., "the downvoter", "those that upvoted this" etc., in ways they might not complain about user that are identified.
The rationale seems to be that since they necessarily do not know who they are even complaining about, it's not such a big deal. However, the comment might still be read by the targeted user(s), other users that know that they do similar things, other users that actually find what is complained about a good thing, other users that just don't like rude complaining out of principle, etc.
All those might be negatively impacted by such a comment. And, even if somebody convinces themselves that they all deserve this, this seems hard to maintain for the last category, which is I think quite sizeable.
When moderators see such comments or are alerted to them, we certainly will remove them. However, as pointed out in the answer, this can take some time, and even if it would be instant it still takes some effort on our part.
Thus, I think we should adopt as a principle for commenting, not to write anything targeted at somebody or some group, but nobody in particular, that we would not also write with an @-notify to a particular user.
Of course, some users will also write rude complaints to particular users. But that's a problem for another thread.