[Dovecot] antispam plugin and seen status?

[Dan Swartzendruber]

I am using the antispam plugin and am very happy with it.  I also have a 
default sieve rule that I found online somewhere that says if you see a 
message that is flagged as spam and not reclassified as innocent, to 
mark it as seen and move it to the INBOX.SPAM folder.  That too works 
just fine.  One annoyance is that spam I retrain by dragging to the spam 
folder is not being marked as seen (I think I understand why, based on 
the sieve rule.)  My question: is it possible to configure the antispam 
plugin to do this for me?  Or do I need a rule in sieve to detect that 
case and just set the seen flag?  If the former, how?  If the latter, 
I'm not quite sure I understand the sequence of events that takes place 
when a message is dragged from, say, inbox to spam folders.  e.g. at 
what point is the antispam plugin invoked vs the sieve plugin?  Thanks!