On: Why is printing “B” dramatically slower than print...

[giomasce]

My first guess was that for most fonts the glyph "B" has splines, while "#" does not (only segments) and in line of principle rendering splines is more expensive than rendering segments. But probably this is nowhere that relevant.

[bjterry → giomasce]

According to my understanding, the rendered character is cached by the OS, so this probably shouldn't have any effect.

[misterdata → giomasce]

That was my first thought too, but I expect glyphs will probably be cached for a while after being rendered, which should make any difference in rendering speed negligible.