I often see replies that are being marked as answer without a vote-up. As I consider accepted answers as useful, I was wondering whether it would be possible to implement an automatic vote-up when an answer has been accepted.
This was discussed on MSO. From the accepted answer:
The latter user has 10 reputation. The right to upvote is earned at 15 reputation.
Therefore, this proposal doesn't make a lot of sense for the type of users you're talking about.
As this came from Jeff Atwood, it is safe to assume it is a canonical answer.
See also, Accepting answer without upvoting?, which has a Status Declined tag on it.
To add to what MPD said, I think that automatic vote-up should not be implemented.
While it makes sense to automatically down-vote spam posts, an automatic up-vote for an accepted answer would be something the OP decides to do. Accepting an answer already gives 15 reputation points to the user who answered; if the user who asked the question thinks the answer deserves extra points, that user can also up-vote it, but accepting an answer doesn't mean the answer is worth an up-vote. If the answer is then that good, it will surely get more than one up-voted, and that automatic up-vote would not give much to the answer.
Considering that the accepted answer is always shown as first answer, independently from its score, I don't see what the automatic vote would take, apart from the extra 10 points the answer would surely get in other ways, if it is really a good answer. The only case where the answer is not show as first answer is when it is written from the user who asked the question.