As stated in the bulk message, we get frequesnt quirks of window sizing due to window geometry hints, but you do not mention checking that.
Do you have window geometry hinting turned on? I suspect that might be causing setting the window to a slightly smaller size based on how many chars are displayable. Try turning it off, and retrying maximise.
If this prevents the border, then it seems this is specific to KDE.
As stated in the bulk message, we get frequesnt quirks of window sizing due to window geometry hints, but you do not mention checking that.
Do you have window geometry hinting turned on? I suspect that might be causing setting the window to a slightly smaller size based on how many chars are displayable. Try turning it off, and retrying maximise.
If this prevents the border, then it seems this is specific to KDE.