Is there an option to change (specifically, enlarge) the default font size across the forum, not just on my profile? If not, could such a thing be added?
You could always use the "zoom" feature on your browser...? Unless you mean specifically for your posts... which I wouldn't recommend changing the font size anyway xD
I know, but that reduces image quality and, in some cases, messes up layout. I've set the default font size for my browser higher than usual, but depending on a site's settings that doesn't always have an effect, and it doesn't seem to here. I mean for all posts, and other text. It can get annoying if someone uses non-standard fonts in their posts, so I don't intend to!
In Firefox clicking View > Zoom > Zoom Text Size only will just zoom the text (good enough for me, but I know on some size it can break the layout). If you know a fair bit of HTML and the likes of Firebug/Inspect Element don't scare you then the Stylish Addon for Firefox is awesome, allows you to amend the stylesheet of a site - I use this on some like Huff Post which use a font I find unreadable.
I am on Firefox, and didn't know that about text-only zoom. That works -- thanks! I don't know much HTML, so getting that addon won't be a priority; the only ones I use anyway are AdBlock, NoScript, and FontInfo.