Yes, the terms "bennyvacantist" and "resignationist" are really not correct English form, and yes it bothers me too, but I think we're stuck with them.
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I guess we could say "Bennyoccupantism", but other people on this forum have already provided shorter and more convenient terms than me.
I just think that people wanted to come up with a shorthand, even if a bit inaccurate, for this:
sedebeneplenebergogliovacantismI think that "nonresignationists" would work also, though, since everything hinges on whether Benedict actually resigned ... but I think people want to cast this as a variant of sedevacantism vs. sedepleism, so they felt the need to get either "sede" or "vacantist" in there somehow.
I think that another term that might work would be "sedimpeditists". Bergoglio was impeded from occupying the See by virtue of the fact that Benedict was still in it.