Right now, my enchanting is at 85. I'd like to train it to 90 before continuing to level it, but no matter how often I check the Temple of Dibella in Markarth, the sisters are always communing with Dibella. What do I need to do make them stop communing?

You should go in and ask them how much longer it'll be.

Forever. Put yourself in their robes... A half dozen hot chicks worshiping the goddess of beauty... Then along comes some hairy Dovahkiin shouting and scratching and asking if he can vendor these twelve ebony warhammers he found...

Personally, I'd keep the door locked too.

Until someone picked the lock.

Lockpick the lock to the door of the inner sanctum of dibella sanctuary or steal the key from the priest, your call.

I entirely did not expect this to work. I decided to break in for the kicks only to find that they're willing to "put me to use" instead of offering the usual punishment of "quick death." Thanks.

Edit: Strange to note that their "communing" consisted of them sitting in chairs, staring at a table. :/

Well, my advice is:

Don't sit on those chairs, can be dangeours to your health XD, sry had to troll this one