Yes and no. Yes, we indeed used and afaict still use the thunderbolt for contradiction in my German university. However "perpendicular" and "bottom/falsum" ar

Yes and no. Yes, we indeed used and afaict still use the thunderbolt for contradiction in my German university. However "perpendicular" and "bottom/falsum" are two different Unicode codepoints with very similar glyphs. https://en.m.wikipedia.org/wiki/Up_tack https://en.m.wikipedia.org/wiki/Up_tack