I'm not unduly concerned about the change in forum text size, it just looked different and I was wondering if it was just me - or, more accurately, the machine. Having now had it explained I'm happy; it is indeed a little easier to read.
That said, however, have you checked out the files pages? The increase, albeit slight, has had, I feel, a slightly detrimental effect on the the bold italic header; e.g. . . .
[Link: flickr.com]