We can deny voting if someone is a scammer or spammer. A downvote is an upvote, but in the opposite direction.

Sending 3 SBD to @buildawhale with the post you want to promote in the memo is "submitting a bid". For new users our smaller @ipromote bot is likely better suited as it is only 0.500 SBD minimum bid.

You can vote with 0.50 Steem power, but to be able select 0-100% how strong your vote is, you need about 480 Steem power than you can cast smaller votes more often.