Possibility to use bolds or italics on "imported from blog" message

No – FB don’t support formatting in posts made through the API. Unless they’ve changed something without telling people.

OK thanks.
Would it be possible though to add a
line to break line between the [imported from the blog] message and the actual content of the comment (%description% tag)?

In other words, have something like this on FB:

“[imported from the blog] XXX wrote :
%description%”

instead of :

“[imported from the blog] XXX wrote : %description%”

If you put blank lines in the comment structure box it will use them. As you can see here:

Please read the section on comment structures in the user guide.

Thank you