Just in case it helps.
Qt is a real headache with unpredictable rendering errors. I thought the risk was only there if you were using QSS, but apparently not.
If you look closely at your screenshot, it's not a space issue, but a font anti-aliasing problem. Look at the left stroke of the D; it hasn't disappeared. It's a very light cyan color.
I don't remember if qt6ct had font anti-aliasing options. Or maybe changing the font there will fix it.
Just in case it helps.
Qt is a real headache with unpredictable rendering errors. I thought the risk was only there if you were using QSS, but apparently not.
If you look closely at your screenshot, it's not a space issue, but a font anti-aliasing problem. Look at the left stroke of the D; it hasn't disappeared. It's a very light cyan color.
I don't remember if qt6ct had font anti-aliasing options. Or maybe changing the font there will fix it.