I think I have finally understood why some people have problems with the direct links to specific posts I have been posting:
If a direct link to a forum post is generated, the URL follows the pattern:
However, the page number count depends on the user settings for posts per page, so the result is not always the correct post.
For example, if I try to link post #70, it's on page 4 for someone who uses 20 posts per page, but on page 2 for someone who uses a 40 posts-per-page display.
This also affects Google search results for this forum: I have set the forum to display the maximum number of posts per page, and if I use Google to find a post here, clicking the link with the search results usually takes me to a completely wrong location in the correct thread because Google builds its links for the default number of posts per page.
I hope my interpretation of what I'm seeing is correct. I have to admit that I don't see an easy fix for this - it's probably something the forum software programmers would have to address, not something the forum administration here could handle.