> I would however complain that the default terminal on macOS is really not very good and I always install iTerm2...
Apple’s terminal is one of the very few that passes the VT torture test and has support for double width and height attributes. Sadly, it doesn’t do overlines and doesn’t italicise my terminal font.
I think it depends on a font supporting them correctly. I’m using a zsh prompt that uses them and it seems normal. Check https://github.com/rbanffy/3270font and let me know if it helps. I was thinking of adding the powerline symbols to the test renderings.
The problem is not with font glyphs, but with colors. Background and foreground colors that should be the same aren't, they are different shades, thus some themes (such as powelevel9k/powerlevek10k) appear broken, see https://imgur.com/a/HAcE4Yu
And the line height -- it could be font, it could be terminal, I didn't investigate (it is DejaVu Sans Mono for Powerline).
Terminal allows fine tuning the spacing. I tried to optimise my font to look good on the default settings, but that doesn’t always work and never works for every program.
Apple’s terminal is one of the very few that passes the VT torture test and has support for double width and height attributes. Sadly, it doesn’t do overlines and doesn’t italicise my terminal font.