Hmmm. So many questions, so little time. In general, I see no problem with re-posting lyrics for the sake of discussion, but it should be made clear that the lyrics came from the DT or from another thread. It's ALWAYS important to identify the source when posting lyrics.
In general, the principle with MUSIC information from other sites is to copy-paste the entire text of whatever it is - within reason, of course. For non-music information, post a summary or excerpts, plus a link.
For Youtube stuff or other online audio or video, I think it would be good to post a summary of the information shown in the link. That's probably true for ANY information you link to - summaries are good. That especially goes for YouTube, because some of us rural hicks don't have broadband and can't access YouTube.
-Joe, Thank God I'm a Country Boy-