still looking for an mail-style quote-pasting add-on

I am still looking for an add-on which can insert text from the
clipboard in email-style (using a quote-marker down the left column),
but which allows me to vary the quote-marker easily .
This should be for both FF (paste into text fields) as well as TB (paste
into emails)

Background:
I quite often have to insert copied text into either web-interfaces,
where I want to have a mail-style quoting and also into
forwarded/responses to emails, where I want to distinguish pasted
text (from an external source) from what is quoted from the original email.

So I want the quotes the 'reply/forward' function inserts to stay using
'> ' as their quote marker, but I would love for text inserted by
copy/paste afterwards to be marked by '| ' or such, so that it is
clear what was in the mail forwarded/replied and what I added from outside.

Sadly, there doesn't seem to be any way to do this currently and I end
up using 'paste quoted' and then hand-editing '> ' to '| ' for inserted
text, or inserting the quotemarks in FF (after removing [quote][/quote]
tags.

I have no experience writing add-ons for FF/TB, so making my own would
be hard (though I might be able to amend from some other add-on that
does something similar, though I haven't found a good starting point nor
a good instruction manual for writing one's own yet).

Any help is appreciated.