> 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. Not to mention that usually the selected part is "broken" html because not all tags are closed.
You also have to ask, when an application puts HTML data into the clipboard, what data it is actually putting there. When I select a section of text, pictures and whatever in Firefox and copy I get HTML data in the clipboard. But Firefox can't just put the source of the document from the point where the selection begins to the point where it ends into the clipboard, as it is announcing HTML data, and as you point out, that wouldn't be HTML, it would be broken HTML. So Firefox has no choice but to massage the HTML data anyway, and if it is doing that already, adding the style information inline is no great hardship.
Of course, if you want to reuse that data as is as HTML for some other web page then you are probably out of luck, but if you think of it that makes no sense anyway - if you want to do that you should probably be copying the source of the HTML as plain text. If you select and copy part of a page in Firefox, chances are that what you are actually about to do is to paste it either as plain text (the text visible on the page, not the HTML source) or as formatted text into e.g. OpenOffice.
And if you were copying the data inside some visual HTML editor, it would probably still not make sense for the editor to insert the data as naive HTML - chances are there would be no way to paste the data in any form resembling the source of the page the editor was generating, and in any case, if you were trying to get at the generated source it would make more sense to ask the editor directly than copying and pasting to get at it. In fact I would expect the visual editor to use some internal format which was not valid HTML at all when copying to the clipboard, but which another instance of the editor would know what to do with when pasting it. It might provide a filter to convert it to HTML, but not for the purposes of viewing the source - you don't use the clipboard for that - but rather as a stepping stone for converting it to OOXML or something else.
Hope that made sense, as I am rather short of sleep currently. I would really like to be clear that I am not trying to argue for the sake of arguing here, but rather because responding to the points you make forces me to think things through myself.