My present configuration: Stock Diablo MicroB + FlashBlock, no "Fit to Width", and 100% zoom unless otherwise specified (EDIT: And full-screen, too).

OK, takes 33 seconds to completely load the whole front page here. This site seems to be designed for 1024x768, so it just almost fits on-screen at 80% zoom, but not quite. And it's big and image laden, so drag scrolling's not exactly snappy. But it works.

Hit the forums link at the top, and it loads in <20 seconds. Individual thread loads completely in ~15 seconds. (And scroll nicely.) At 100% zoom, the entire thread (text + avatar/etc.) fits in the browser width. For me, the text is quite readable...

At 120%, you do lose the avatars (unless you scroll sideways, too) but can handily keep the text on-screen. (Font is perhaps somewhat easier to read, but not much.)

At 150%, you have to align things very carefully, but you can read down the column of text with no horiz scrolling; now, though, the finicky alignment is making it hard to dart over to the left for avatars, so it's rather unusable. The text is getting huge now, but for me, it's no easier to read than at 120%.

Just for kicks, I threw together some css to "fix" it. It's not optimal, and has rather ugly results, but it helps...
You'll need to put it in .mozilla/microb/chrome/userContent.css. (More details...) It right-aligns the avatars (and user info with them) and makes the font 150% in the text. Now zoom up to 120% works with a good chunk of the avatars (and all but lengthy usernames) on screen, or 100% is comfy reading. There's a screenshot of this at 100%...

Finally, I tried applying "Fit Width to View"; it now takes 15s to load the thread page, and then 7s to reflow everything, leaving the actual posts down below all the ads... Not good. Zooming, of course, takes 7s each time, blows the avatars way up, and drops them after the corresponding posts. But no major page rendering breakage occurs up to 300% zoom, for me, so I can still read just as easily (after the initial wait) as before... (Are you running Diablo, i.e. did you flash the device since you got it? They may have enhanced this there; it doesn't seem near as bad as I had remembered from previous versions... As I said, I almost never use FitWidth, as it tends to break most anything but plain text. OTOH, it can be handy for reading online books...)