I’m not sure what I did, but at some point today I started seeing the default font in the body of posts appearing larger than it had before. This only affects the post text itself; to my eyes the main forum index and the topic listing in each subforum looks the same. Setting the forum preferences font size to “Smaller” gets the post text back to the way it looked before, but the main forum index becomes significantly smaller. It’s like the post text size has somehow become disconnected from the text size of the rest of the forum. If there’s some setting to change that, I haven’t been able to find it.
I’m viewing the site on MIcrosoft Edge. I double-checked, and the browser is set to default 100% zoom. I haven’t done anything to customize the browser font size, unless I accidentally hit some arcane keyboard shortcut and changed it without knowing.