If you click the link icon under a reply, you’ll see that the URL ends with a parameter whose name is u and value your user name. What is that about? I always end up deleting it when I paste the link into a document of mine (as when adding the reference where I have copied a reply’s code into a script of mine).
Also, I note that you can delete the number at the end of the URL if you want a link to the topic itself, rather than a specific reply, but can’t do that if you include the number of the reply at the end.
I’m surprised the topic-numberless URL works at all, I would say it is mostly invalid. Almost certainly it will break if the title of the topic changes, and it would definitely fail for cases where two topics have the same title.
The topic number is the URL, the slug before it is just for appearance.
Peter, I believe you’re correct. I’ve been saving the links to the topics for the macros I’ve posted, and as long as I include the topic number in the link, the links work even if I change the topic’s title.
When I’ve finished reading through the posts in Mail, I just look through the notifications. Mostly they are just likes, or occasionally replies or whatever which can be helpful if I’ve missed something in a topic I’m just scanning (eg the JXA/ES5/6 topic which I just skimmed, but if someone asked me to comment on a particular issue, then the notifications would catch that).