I thought this was a regression, because I compared a Wikimedia wiki history page with one on my localhost but that was due to bug 29778.
Currently text becomes confusing or unreadable in diffs during the use of <ins> and <del> without fighting the browser defaults (strking and underlining). See attached screenshots to see what I mean.
We should add default styling to prevent that.
Version: 1.17.x
Severity: normal