On Stack Overflow proper, you must have 50 points of reputation to comment anywhere on the site, not just on your own posts and answers to your questions. However, on Meta, even 1-reputation users can leave comments everywhere.
This is done on SO and everywhere else to prevent spam, like the following comment I just deleted on Meta:
Note that this comment stayed on the site for 7 hours before it was finally detected and removed.
Our current anti-spam and anti-trolling system appears to block normal posts (questions and answers), but the spammers and trolls who were blocked by this are now using comments on Meta to work around this. In addition to the above, at least two trolls have used this to post off-topic and sometimes very disturbing comments to random posts over the last week here.
What is the use case for allowing brand-new users to post comments anywhere on Meta? Should this privilege be brought more in line with the reputation requirements of Stack Overflow proper?