> On the reply pages, the HTML for each post is on a single line.

Oh, my mistake then. At a glance, I thought that everything was on a single line for the reply pages too.

> On the main page, it just ends up on a single line because the templating code strips all newlines to make it possible to get the individual posts on single lines.

I don't follow that logic. I tried looking in the Perl code for answers, but my possibly-mistaken interpretation says that when someone posts, thread pages are generated/updated first, then the main page is assembled from those. How does putting everything on one line on the main page have any effect on the thread pages?