See that space adding on TranslateWiki: the space is not highlighted.
Whereas it works well on Wikipedia.
As far as I know we are not using wikidiff2.
My bad, I thought wikidiff2 was part of MediaWiki core, I didn’t know different diff evaluator were possible.
I just checked and it seems, wikidiff2 is really not installed on TranslateWiki. I'll remove the tag. - ( using wikidiff2 might solve the issue ;-) )
The php-wikidiff2 package from mediawiki-lts repo depends on PHP 7.0 for Ubuntu 16.04. I don't fancy compiling it myself. Maybe after distro upgrade.