This assumes people would be more willing to vote on comments after the change.
I've been upvoting comments under my posts almost since the day I joined, which means my initial votes were way below the threshold. It's not a problem anymore now, obviously, but the change would force me to use a lot more VP if I want to guarantee that a comment I appreciate gets anything for it. I rarely see more than 1 or 2 people upvoting a comment. If not at least one of the is a dolphin or voting with 100%, there will be no payout and people have wasted their VP.

I get where you're coming from with your proposal. But imo, it would accelerate the death of this platform. Spammers have to be dealt with (I flag them under my posts all the time), but not at the cost of hurting minnows.