Sometimes when I login, the panel (or at least, the task manager?) starts with a nice, small font. Other times, I get a large one. Long ago, this was caused by plasma crashing on login, and restarting (I think). It seemed that at first it had the small font, but when it crashed and restarted, it had the large font. I see no evidence that it's crashing now, but I don't understand what's going on. I would like the small font, so I have more real estate.