I suspect the <font-size="-1"> represents an attempt to minimize the number of continuation lines. If so, it may have been -- in the days of 800x600 displays -- a reasonable design choice. However, it would be more amenable to user-override if rewritten with css.

And generally, to those who feel that control of the rendering is a "user right upon which PM should not intrude," so to speak, I see no way that specing a more readable font in any way restricts that right. The intent and, ISTM, the effect would be to assist those whose knowledge does NOT include "how to create a local style."