Players have used the word "gaymer" in their IGN primarily because of a famous YouTuber. Some just use it because it looks cooler than gamer. But no, it's not offensive. The only reason you need to mask gaymer for gamer is because we all know that people insult others with the term gay. It has been overused and it can no longer be said because of those immature 6-11 year olds. Therefore you can't say gaymer since it includes the word gay. But it's not bad having gaymer in your IGN. If you have any more questions, feel free to contact me.
~Locked