Everything you said about questions applies equally to answers. 
A few days ago I posted a one-line answer
(to [this question](http://superuser.com/q/813728/354511)) because I was in a hurry. 
By the time I got back to it, 15 hours later, it had accrued two downvotes
– as far as I can tell, simply because it was too short (lacked explanation). 
I proceed to expand on the answer, so it’s now over 50 lines long. 
I engaged in several rounds of comments with the OP, who eventually accepted the answer. 
But the downvotes remain,
(presumably) because the downvoters never realized that I had updated the answer.

Since my initial answer was *correct*, but just code-without-explanation,
I would hope that people would have used conditional downvotes if they had been available.