HTML tidy moves whitespace around, including in some cases where this is not desirable, for instance:
"<span class="geo-multi-punct"> / </span>" is changed to " <span class="geo-multi-punct">/</span> ". This is not desirable because this span is "display:none" for most people, but HTMLtidy makes the spaces show up in elements that are visible by default. The only way to fix this atm seems to be to use "<span class="geo-multi-punct">﻿ / ﻿</span>", which is terrible of course. It would be nice if this part of HTMLtidy could be disabled, since it is supposed to be non-visual cosmetic cleanup done by HTMLtidy, but turns out to be visual in en.wp in some conditions.