I'd like anonymous users to be able to comment only once on a node. I thought about checking whether there's already a comment from the user's IP-adress and, if yes, hiding the comment form, but I don't know how to do that.
How can I achieve this?
When a anon user views a node, call
When a anon user comments, register that as a flood event in
This is the bare bones of how to implement hooks that make use of these functions:
PS: The module Anonymous Publishing is already using this pair of functions to limit the number of comments an anonymous user can post (but not exactly in the way you specify). However, looking at the source code of that module should give you an idea about how to use this pair of functions for flood control of anonymous comments.