Here's the GitHub discussion.

@glenalbrethson is correct, this is a modification to the dust vote threshold, not the dust payout threshold.

To have a dust vote you have to be effectively voting with about 1.2 SP, so it won't matter to any existing real users unless they're a new account that has voted down to single-digit voting power percentages.

It will matter to new accounts created under the new system, and the idea that it "improves the user experience" to let users cast a vote that won't be counted is kind of appalling. But once they've been here for a very short period of time they'll get past that limitation, so it doesn't matter a whole lot on a practical level.

I'm not as clear on how the flooring process works and I think it could have some unintentional penalties for high-vote-volume accounts like @hr1. But for most users it should be too small to matter much.