\[DifferentialD] apparently does not have a Unicode representation, so I had to enter it directly in a reformatting of question 83672. However, I noticed that it is displayed in blue, as if it were an unknown variable. A minor issue, perhaps, but I think this should be fixed.
In light of the comment by Histograms, I suggest that it would be better yet for Mathematica StackExchange to interpret and display this character rather than just inserting a blank (probably non-printing) character. The same is true of
\[Distributed] and, perhaps, other Mathematica characters.