Q:

Is it a good strategy for the Seer to reveal his identity at the beginning?

Should Seer take part in the Sheriff contest and indicate his identity at the beginning? 
When I watched a so-called top werewolf boardgame live, this Seer publishes his identity at beginning, he argues with the werewolf who act as Seer with the aim of misleading the villagers to vote someone his claimed as "werewolf". I though this Seer will soon die, but werewolves do not dare to kill him at first two round. Interesting. Killing hims means accepting the fact that he is real Seer. 
I though Seer should keep secret and survive as long as he can, so that to investigate more players. This is a way to keep him safe and time to get more information.
Is it a good strategy for the Seer to reveal his identity at the beginning?

A:

It is almost never wise to claim to be the seer. And it seldom happens. But sometimes it can be a smart move. Especially if another player claims to be the seer. 
If two people claim to be the seer, it is almost certain that one isn't. And that is most probably a wolf. The true seer can check this. And start a discussion. There are three possibilities:

The true seer fails to convince and is killed by the vilagers. Next day, the fake seer will almost certainly be killed.
The false seer is killed by the vilagers. Next night, the real seer will almost certainly be killed.
The vilagers decide not to kill any of those. In that case, if the wolves are killing the real Seer, the fake seer will almost certainly killed by the vilagers.

All three cases link the death of the seer with the death of a wolf. And that is not a bad ratio. Yes you lost the seer. But he took a wolf too.
But beware, sometimes a mean game master can add two seers to the party. And that can become a bloodbath.

