Supercite provides some paragraph filling functions and will
automatically fill paragraphs as they are cited, when the variable
sc-auto-fill-region-p is non-nil (the default value).
There are other packages freely available which work quite well when
filling paragraphs of the non-nested citation style (and probably better
than supercite's built-in functions!) so supercite calls the filling
function via the hook sc-fill-paragraph-hook. The default is for
supercite to call the function sc-fill-paragraph.
You can also have supercite query you before filling each paragraph in
the cited region. This would be useful for citing an article with mixed
code and text, where you would want to fill the text regions but not the
code regions. Set the variable
sc-auto-fill-query-each-paragraph-p to non-nil (default
value is nil) for this feature. Note that
sc-auto-fill-region-p must be non-nil for query filling
to work.
Note further that turning off auto-filling does not preclude you from manually filling each paragraph (see section Post-yank Formatting Commands).
Finally, supercite will collapse leading whitespace between the citation
string and the text line when the variable sc-fixup-whitespace-p
is non-nil. The default value for this variable is
nil.