As a general rule on SE, badges are not revoked if you get one and then you lose the qualification for that badge. For instance a Necromancer badge is not revoked if the 5th upvoter removes his vote, nor is the Electorate badge revoked if one's question/answer ratio drops below 1/3. The theory is that the next time you earn said badge you won't get an extra one and the totals even out eventually.
A few weeks ago, someone upvoted many of my answers that had 9 votes, granting me many Nice Answer badges. This upvoting was thereby removed by the fraud detection mechanisms SE has in place to protect against sock-puppeting.
Yesterday I received my 22nd Nice Answer badge for an upvote to this answer, however, I currently only have 17 answers with >10 votes. Why did I get another badge? Maybe when the requirement for the badge is removed by the vote fraud mechanism, the badge counter doesn't notice it?