Whoops I got it confused. Maybe if you had of replied to my PM that I sent a month or so ago.
I know why you used 'their', but it doesn't make it correct or an acceptable substitute. Don't just butcher the English language for your convenience, especially when you're representing something. Either ask the person his or her gender and use 'he' or 'she'. It's also acceptable to use 'he' is the person's gender is unknown, and most people here are male anyway (sorry if that's not PC xdd). Or you could just change the wording. He are some examples:
'for osu!, we let Baraatje123 pick the maps'
'for osu!, we let Baraatje123 pick his favourite maps'
'for osu!, we let Baraatje123 pick his/her favourite maps'