Bad idea.
There are/were already gentlebot and thing-2.
I have not much grudge against them since I was upvoted by both in the past.
9rumpyc@t's and ch3ckth!50ut's spam comments got upvoted more often by at least one of them.

1. encourages more spam

2. fights the purchased vote trend the way gentlebot and thing-2 still did not prevent me from realizing that a better modus operandi is to get my comments upvoted in a certain way.

3. would be like a lotto so people would be excited if they won - lotteries are usually a waste of resources, and this will be too especially if it will skip bot upvoted comments like gentlebot and thing-2 probably do.

4. could allow people to delegate steem power they aren’t using but not participate in vote buying - and steem power delegations are usually wrong. This will not be an exception since certain delegations provide income to the owners of the delegated stakes.

The reputation should be above 40 or some other level to exclude the most obvious Sybil attacks but the bar would be low e Pugh so they everyone who post would eventually win.

• and by doing so discriminates against victims of bad players and gives the bad players an even bigger chance at winning such a lottery.