TL;DR: Fixed in the next build.
I've made two changes to the diff engine, so once this is deployed it'll look as expected. For reference, this is what you saw and complained about:
And this is what looks like after my changes:
(I've removed the unchanged codeblock from the screenshots.)
The two changes I've made are as follows. First, when separating the text into diff tokens, we no longer consider trailing spaces to be part of HTML tags. This never made a lot of sense, but even less so after this change. The consequence it had was that when, say, bolding a word from
This is very important.
This is <b>very</b> important.
then in the first version,
important has a leading space, and in the second version it doesn't (the space after the
</b> would be considered part of the tag instead). That's why the word "important" was shown as changed.
The second change I made also has to do with the space-as-part-of-the-word thing. For some background why that's necessary I again refer you to this answer of mine, but the short story is that because we don't want this:
until 2013 we got this:
and from then on we did this:
The leading space being added and removed still looked a bit weird, especially in the side-by-side view:
So I've added a post-processing step. After the diff engine has run, we look for a space that appears at the beginning of both a removal and an insertion that occur in the same place, and mark that space as unchanged instead.
And with that, what we'll get from now on is this: