Man, I've come up with better answers in the past, but really, being asked to "reconcile" being a feminist and being a polyamorous kinkster just feels irrelevant. Like being asked "How can you wear baseball caps and also own a cat? Don't you feel like a hypocrite?" They're two such separate things in my life.
It's possible to be polyamorous in a misogynist matter, and treat multiple partners as a harem, as multiple possessions and proof of your "status." (I always like that Rowdy's attitude has never been "I'm dating two women--I'm so cool," but "I'm dating two women--these two women are so cool.") It's also possible to be polyamorous because you're so damn feminist that exclusivity seems like oppressive ownership to you.
It's possible to be kinky because you like an excuse to hurt people and deep down you really don't like them--or because you think you really deserve to be hurt. It's also possible to be kinky because you simply like to play with intense and dramatic dynamics and sensations.
Although it's interesting to note that in both of the examples above, people acting in the unfeminist ways tend to be perceived as just plain bad and generally aren't popular in their respective communities. You may be kinky for bad reasons and maybe that's not going away, but very few people who come to be known in The Kink Community (patchwork as it is) are the bad-reasons type. If kink is neither feminist nor anti-feminist, The Kink Community tends to skew feminist. I'm less familiar with The Poly Community but I believe that they are even more so.
Two things contribute further to this:
1) Being in a sexual minority means that you can't hide behind "normal." Saying "well, gender roles are normally XYZ" sounds a little hypocritical when you're wearing floor-length latex and carrying two hundred and forty feet of lovingly coiled hemp rope. You're in no position to be enforcing the status quo.
2) The kink and poly communities are diverse. Although there are probably horrible little enclaves somewhere for people who only align themselves one way, in most kink communities you're going to run into dominant women and submissive men, in poly communities you're going to run into women with multiple male partners, and in both communities there are queer and non-gender-conforming people. Anyone who thinks kink is about putting women in their place would have that clarified for them right quick after about ten seconds with some of my kinky friends.
Finally, the main reason that I don't worry too much about the feminist cred of my sexual activities is that they feel good. Not "I deserved that and my inner pain has found catharsis" good. Like "warm fuzzies" good. I go to work and things get difficult or boring and I think about the bruises on my breasts, the little cuts healing on my back, and I'm happy. It gives me strength through the day.
I don't have the ability or authority to designate every activity on Earth "feminist" or not, but when something gives me as much simple joy as my sex life does, I'm just gonna go ahead and enjoy the hell out of it.