Does anyone know why the quest limit went up from 10 to 15? Is there an additional event going on?

No, you have a gold account (that gold icon beside your username). Gold Accounts got perks including the quest limit from 10 to 15 :D Here's the full list of GA (Gold Account) perks (Which can be accessed from Cash shop >>> Gold Accounts)

Wow, that's strange, I didn't use a medal or subscribe, can other people give you gold account status, or did I just somehow accidentally give myself a gold account haha? Not that it's a bad thing! Thank you so much for answering,

Somebody might've given you a buddy GA, there'll be an alert for it but you could've missed it ^^

Thanks for the info! I feel a little silly now having not known or noticed that ^-^'

no its fine XD i cant be sure but i think it goes under the "others" alerts, so i mean you could miss it if you blindly delete all the dance alerts x)

That makes a lot of sense XD Thank you again for your help!