In message , Sacha
writes

All groups have their own customs. On this one, full repetition of
irrelevant parts of the post being replied to, are snipped, customarily, so
here your argument doesn't hold water. Of course, none of this can be
enforced and I don't think anyone has suggested that it can be but on the
whole, good manners suggest that people new to a group try to follow that
group's generally accepted ways. A journalist friend of mine has suggested
that groups or organisations which take, repeat and use the posts of others
from the group for which they are intended, may well be in breach of
intellectual copyright and that one of these days and if anyone can be
bothered, they might be open to a law suit on those grounds.

I have noticed that this group is better at sniping than others to which
I contribute. I typed that and saw the Freudian error, but left it
for your amusement. ;-)
Worse still, I almost ended the sentence with a preposition.

I think that once someone starts making threats of legal action it cuts
against the spirit of newsgroups.

IANAL, but for such an action to be successful I expect that it would
have to be proved that there was some loss of income resulting from the
plagiarising of professional and specialised information not available
elsewhere.
I have contributed to groups where people have used their professional
knowledge for the benefit of the group, and this is fairly normal.
There is another aspect to this of course, and threats of action could
be made even when there is no case to answer, if the accuser is wealthy
enough not to care whether they win or lose!
It happened to me, and I have his email to prove it!
--
Gordon H