Sometimes a code snipplet included in the original question is almost working, but not quite, and only requires a small fix. But sometimes it is important to show contextually where this fix goes (rather than just say "substitute X with Y"). As an example, in one of my recent answers the "fix" is only 11 additional characters out of more than 100. I think it will increase clarity if the differences are highlighted.
Is there a easy way to high light code differences?
I ask because in a "code" block, the bold and italics mark-ups are ignored.