[rbanffy]

> I would think they're only supposed to just touch, with no gap, no overlap.

Because of variations on how software terminals and GUIs render fonts, this is very tricky. That’s why so many terminal programs take over box-drawing characters and implement the glyphs themselves. This way the glyphs defined by the font are a rendering failsafe and it’s sometimes better to not even implement them and leave it to the systems font substitution mechanisms.

Hardware terminals had fixed vertical spacing, which made alignment much easier.