The tilde "~" is a mark which appears in the game setup window (and only in this window) after the name of a person who only rarely plays against either players rated lower than himself, or against new players (whose rating is shown as [?]).
It is visible only to the player himself and to his potential opponents, if these are rated better than him or if their rating is hidden (i.e. if they have [-] as a rating). It is not visible to weaker-rated players.
This mark was introduced onto the server in order to allow those players who expect a level of reciprocity to avoid giving games to weaker players who act more selfishly. It is obvious that if everyone were only willing to play stronger players, there would never be any games.
The tilde has several effects:
The exact formula is:
If 2*(number of games against weaker players or ? players) + 5 < (number of games against stronger players) then the player obtains a tilde.
The overall effect is that if you play at least a third of your games against weaker players or against yet unrated players, you are unlikely to obtain a tilde.
Games against players having the same rating as yourself, or a [-] rating, are not taken into account for the above calculation. Also, contrary to what is sometimes said, the colors of the players in a game are irrelevant. The handicap is not taken into account either, nor the size of the board. Games of all types (Free, Teaching, etc.) are taken into account.
Your whole list of games (i.e. all those played in the last 180 days) is taken into account for this calculation.
If you have a tilde, you will normally want to get rid of it, as while you have it you will find it hard getting games against stronger players. To achieve this, it is enough to play some games (of any type: Rated, Free, Teaching, etc.) against players who are rated weaker than yourself, or are new to the server and rated with a [?].
If you have had a tilde for a long time, it may take you longer to get rid of it. You will need to play enough games to increase the proportion against weaker or [?] players to more than around one in three.
