How do suggested edits work?
While I've been approving suggested edits, I've seen many times that edit is proposed by an anonymous user. What is meaning of that? Most of time it's invalid.
Anonymous visitors (anyone not logged in) can also suggest edits.
A lot of the time they mis-use that feature to make a comment or ask a question, these edits should be rejected outright.
I suspect you are confusing 'approved' with 'suggested'. Do you have any examples of such suggested edits actually being approved (e.g. accepted by reviewers)? If so, please roll back such edits.
Yes, we sometimes get crap from anonymous users this way, but there are also good contributions that come in this way, that we do not want to turn away. 37% gold is worth a lot, see Do we have stats showing that anonymous edits are helpful?.
Thus, removing the feature for anonymous users has been turned down before, see Prevent suggested edits coming from anonymous users?.
Anonymous users are allowed to suggest improvements to posts like any user.