The sum of the widths for the coloured-bars and textual parts of the
display is greater than the default width of the X window: the two
overlap by a letter-width or two (so bits of text with matching
foreground and background colours disappear), and the lines from the
coloured bars to their captions end up leaning backwards, until I pull
the window a bit wider.  Should the total width be greater, or the
width of the coloured bars be less? or should the window auto-adjust
itself to be at least sufficiently wide?

It's more of an annoyance than a bug, so perhaps this should be
moderated down to "minor".

Not shown below: using fvwm 2.2.5-1.1 under xdm 4.1.0-5; by eye, the
(default) width of the frame sides is about half the width of the
overlap.