In a comment on a recent entry , Verisimilitude noticed a feature that I quietly added to here not too long ago:

I've noticed the Add Comment button is now conditionally excluded; that's a neat trick.

I've long had precautions against comment spam and they've mostly worked. But not entirely, and so there have always been some network areas that I disallowed comments from even if they didn't run into those precautions. And if a (bad) network area was a sufficiently high source of automatically blocked comment spam attempts, I would add it to the list of blocked areas in case the software doing the comment spam got smart enough to get past my other precautions.

For a long time the only thing this blocked was direct access to the specific URLs used to write comments here (where the 'add comment' links point to). Then, recently, I realized that it made very little sense to give people and their software the link then block them when they used the link, and it would be better not to give them the link in the first place (as well as still blocking direct access). Among other things, I can hope that this stops software from crawling Wandering Thoughts to collect all the 'add comment' links that it will hit later through, for example, a proxy network.

Adding this feature was made easier because DWiki , the wiki software behind Wandering Thoughts , already had a permissions system for whether or not people could leave comments (and who could). As part of that permission system, DWiki had always done the obvious thing of not generating an 'Add Comment' link unless you had commenting permission. So all I had to do was extend the permissions check a little bit.

(The actual implementation has a collection of markers that can be set during processing of the request to influence what additional links are provided and not provided. For example, if you're a known robot, you don't see links to my syndication feeds because I don't allow known robots to request those. So I have a whole set of what is effectively middleware that scrutinizes the request and decides what should be allowed and not allowed, and then the final, low level dynamic page rendering looks at the result and includes or doesn't include various things.)

So if you visit Wandering Thoughts entries and they don't include an 'add comment' link, that's a sign that something about your request is making my anti-various-things precautions block comments (it might be your IP address or it might be something else).

The general idea strikes me as obvious in retrospect. If you're going to block direct use of something for some request source, you almost certainly want to not serve links to it either. And it's probably a better and less frustrating for any innocent bystanders caught up in a 'you can't comment' area. Previously it would have looked like they can comment, but any attempt would fail; now, they don't see the link at all so they can't get mysterious failures.

(Fortunately, DWiki always blocked all access to the 'add comment' link, even the initial one, so no one ever faced the really frustrating experience of writing a comment only to have posting it fail mysteriously.)