Playoffs are coming in my world and it looks like I'm going to make them.  I'd like to take advantage of collective wisdom and ride off into round 1 minus one pitcher and plus one position player.  My 12th pitcher (the one I'd like to remove from the playoff roster) is:

http://whatifsports.com/HBD/Pages/Popups/PlayerProfile.aspx?pid=1923506

The last time I demoted him, as you can see (season 17), he took a pretty solid hit.  Are the rules for playoff demotions different? Or...I currently have a position player on the DL who will be back by round 1.  Could I use his reactivation as a tricky way to move the pitcher without a demotion hit?

You don't have to demote him to remove him from the playoff roster.  I'd carry 25 players no matter what. 

Awww shucks.  I was wondering where the button was for playoff roster management was.  Just found it on the Roster Management screen--an entirely logical place for it.  As is obvious....I'm new to the playoffs.  Can I put minor league players, who are nevertheless on my 40-man roster, onto the playoff roster without them accruing ML-service time?

You can.  However, if the WS ends with them on the roster, they'll start next year at 327k.

Quit helping him. He's one of the teams I'm chasing for the WC. ;)

Hbdgirl, this is your chance.  The Tiger Sharks and the Pheremoniacs can't keep losing for long :)