There are about 50 quoting related bugs known -- among others: wrong quoting for quotes, hyperlinks and lists.
The list related quoting bug is very similar to what I report in this topic (even though the wrong layout is a bit different). It was reported about 1 year ago.
Seeing this huge number of quoting related bugs gives me the feeling that something is fundamentally wrong (i.e. on the conceptual level): it looks as if "partial quoting" (in contrast to the quoting of a complete post) were using the same approach as that used for moving information from the browser into a different application: tell the browser to put the text (without layout) into the clipboard and take this text out of the clipboard at the target location -- as the target application cannot be assumed to understand html markup, the browser will place markup-less text into the clipboard -- and consequently, large markup parts are lost. Looks as if something like this happens at least for "partial quote"s.