Character does not scale properly as font size changes

One possibility is that the APL385.ttf font entry for diamond is either wrong,
or has some subtle problem that causes gnome-terminal to get the scaling wrong.
The font is available here:

 www.dyalog.com/downloads/fonts/Apl385.ttf

Attached is a screen shot from Open Office. In that, you can see that
the diamond character displays correctly at different sizes
(i.e., slightly larger than the iota and rho) when using Times New Roman,
but displays much smaller when using the fixed-width font.

From this example, I see that the problem does not really lie in
scaling (because the fixed-width font also scales, as we can
see when looking at 12pt and 40pt), BUT the character is being
rendered considerably smaller than it "should" be. I.e., it should
fill the line.

This comment from the creator of the APL385 font may shed some
light on the cause of the problem:

"Diamond is a BIT odd as it comes from the geometric shapes block,
not the maths area of the font. "