It has changed multiple times, but the system is provisionally settled at this point.
First the OGS rating to rank conversion formula from the new ranking update is used to convert the player’s overall OGS rating to a rank, which is then multiplied by 14 (subject to change if this proves to be too high as Sensei’s implies) to convert to points rating. This is performed anew each round to maintain correspondence with OGS ratings. Each player has a “rating offset” which is persistent between rounds and increases by one for each win, decreases by one for each loss, and can be manually adjusted by request (subject to approval). Before pairings are made and reverse komi values generated, the points rating and rating offset are added together. What players see as their rating, it should always be this sum (plus a constant to make most ratings positive, as otherwise all kyu players would have negative ratings). I also try when relevant to provide the offset, but that is already taken into account in the rating displayed to the user, so one can ignore it if uninterested.
Once all players for the round have had their ratings (including offset) calculated and pairings generated, the reverse komi for an individual game is calculated by finding the difference between their ratings (including offset), and giving 7 points to White.