Would applying silicone grease to an EPDM seal/gasket be helpful or hurtful?
Overall I don't think the grease would hurt but may have made the repair more challenging; greasing the seal likely would have improved the watertightness, but also may have made it more difficult to install correctly (the seal needed to sit in a groove and be slightly stretched).  It also would have added a slight chance of grease getting onto the clothes.  Considering that the original seal was ungreased and still watertight after 8 years I decided the risk wasn't worth it.

PS) In case anyone else is doing this repair... After bolting the drum together I was extremely alarmed that the two halves didn't seat together cleanly.  The seam was tight at the bolts, but in between the bolts there were gaps of more than 1/16th of an inch--O was sure I'd pinched the seal and almost took it back apart.  Thankfully I found a few high res photos and videos and it appeared this is normal.

So, if possible, take photos of this seam before disassembling it.  Also, be sure to clean the channel this seam sits in very well.