I went through 7-8 pages of search results and nothing came up, so I'm putting this here.
While most posts aren't linked back to often, for ones like the Watch Challenge or its Discussion thread are frequently visited, edited in the first case and referenced in the second, having stable permalinks is important...
However, as someone IN that discussion thread pointed out, whenever someone takes a post off or one is deleted (whether a duplicate, spam/other inappropriate sort of post, or put in the wrong thread and moved, etc), the post that moves from the first post of page #X will suddenly be the last post of page #X-1 and the permalink, because of how it's coded here, dies. For something 35 pages long, if, say, 6 posts are removed, that isn't just 34 people whose posts get new numbers, it's 34x6. If a whole lot of spam is cleared out of a post, you could have someone's post change pages multiple times, and if it's an info-rich post, they may not want to have to find it over and over (or more likely have a dead post link someone eventually tells them doesn't work).
We EITHER need deleted posts to simply be "phantom" posts, invisible ones that simply make 1 less post on that page with the link format staying the same OR we need the link format to follow how most forums do: ignore the page number and simply go to the post wherever it may land. I don't see why the page number is needed, but I'm not coding it here, so I don't know the reason behind it... I DO, though, know that while it would likely be a better LONG-TERM solution, it's probably a much more TEDIOUS one since every single long thread would have to have its posts reformatted... whatever's easier OR whatever y'all deem a better option, when a permalink crashes because some other post was deleted, a lot of users will think they've had their post blocked/removed since that's usually why you can't find something in a thread, not what anyone wants rule-following nice challenge/bingo participants asssuming.
There are other ways to do it, but those two seem like the most sensible ones *I* thought of immediately. I think the phantom post option is easiest-turn it into a blank post with no detail but that link staying there. I've seen forums do it that way, too, and it may have a double-benefit here in that someone taking deleting the first post won't make all the posts under it disappear if it has a lot of discussion happening-in that case it'll often SAY the post has been deleted so that replies to it (when they depend on that post remaining) do not get deleted (or taken out of context-either way).
Not a super high priority but people don't really know why their posts disappear (or even how to find them when they do) because most sites don't make the page part of the permalink, only an option to go to the top of if you're browsing.
