But junk would be completely expected in this case, wouldn't it?
The simplest option would seem to tag these mixins somehow to make them obvious and, perhaps, allow opting out of this altogether in the account settings.
I'd urge you to try it again, but on a large scale. I know I personally would tolerate one questionable entry on the FP if it frees me from the need to do the /new duty.
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(Edit) I should've not said "mix a random story", but rather "show a random story", somewhere on the FP, at a fixed place and clearly marked as such. This is
it.