I've had a few [1] posts [2] make it to the front page of Lobsters [3]. Lobsters supports webmention [4], yet I never received a webmention for those two posts. I checked the logs and yes, they were received but I rejected them with a “bad request.” It took a bit of sleuthing, but I found the root cause—the URL (Uniform Resource Locator) of my post was, accoring to my code, invalid. Lobsters was sending in a URL of the form https://boston.conman.org//2023/01/02.1—notice the two slashes in front of the path. My code was having none of that.
I'm not sure why Lobsters was sending a URL of that form as previous [5] webmentions [6] worked fine, but when I checked previous submissions to Lobsters [7] I saw some of the links had a double slash in the path portion. As it's considered valid by the What Working Group? “living standard,” [8] I ended up having to accept what I consider a malformed URL.
Sigh.
[4] https://www.w3.org/TR/webmention/
[7] https://lobste.rs/domains/boston.conman.org