> Problem is that in the case of html, you generally lose the formatting information because that's not in the part you copied, but higher up or in a css file. So there is no native format, you don't want to copy raw html code into a word processor, nor the plain text, but something that more or less looks like what you copied.
Just for interest I copied some text in Firefox and ran my clipboard format viewer. Here are the results:
$ ../tmp/viewclipformats
Found clipboard format: TIMESTAMP
Found clipboard format: TARGETS
Found clipboard format: MULTIPLE
Found clipboard format: text/html
Found clipboard format: text/_moz_htmlcontext
Found clipboard format: text/_moz_htmlinfo
Found clipboard format: UTF8_STRING
Found clipboard format: COMPOUND_TEXT
Found clipboard format: TEXT
Found clipboard format: STRING
Found clipboard format: text/x-moz-url-priv
Without knowing, it wouldn't surprise me if one of those contained both the html and the formatting information, which I think should be feasible with my proposal too.