I found at that having amaroK submit tracks that are played as
part of a stream is against last.fm policy.

However, maybe the following alternative solution could be used:

Manual submit of metadata. This would allow the user to edit out possible stream cruft, and also of course the user won\'t normally submit possible advertisements.

amaroK currently already shows the metadata, a possible implementation
could be that you click the metadata it shows, and you get a new window where you can edit the meta-data and a submit and cancel button.