There's two main problems. One is with underlines. Underlines don't consistently appear, and when switching windows they may spontaneously appear or disappear. Furthermore, when clearing the screen, underlines don't always go away with the text that was underlined; sometimes the underline remains without any text there, so I get seemingly-random horizontal lines on the terminal.
The other issue is with Unicode characters. Unicode characters that aren't in the font I use (PxPlus IBM VGA8, from here) show up cut off at the bottom of the line as the height is adjusted. Even worse, the height isn't reset, so subsequent characters on the same line appear cut off as well, and don't line up with the beginning of the line.
I've noticed that turning off bi-directional text rendering in Konsole has an effect on this, but it just replaces it with different incorrect behavior: underlines don't show up at all, and Unicode characters (along with the following non-Unicode text) are shifted up instead of down.
Here's a sample of the incorrect behavior as seen in Konsole:
And for comparison, here's
gnome-terminal with the same font settings, which displays correctly:
Does anyone know what causes this issue, and how I can fix it?