Board Game Arena

In a game of 4 players, when one asks a question, he also gives the answer to the question chosen while it is not the case with 3 players (nor 2).

This is odd and it kills the strategy of asking a question you don't want to answer yourself because it would give too much information on your code, and it favours even more the fourth player.

Anyone knows why the game behave like this with four players? Is it a bug?

Have your read the rules? The rules summary says: "on 4 players, you also give your answer". The linked English rules says "Remember that all questions are treated as [Shared Info], so all players including yourself must answer them". It doesn't look like a bug.

In a four person game, your strategy could be to choose the question that gives the least amount of new information as opposed to the one that gives too much info about you (as in 2,3 player)