What does XD mean? People keep 書く that in the コメント and I don't know what that means.

It's a smiley that means you're laughing really hard. If あなた tilt your head, it looks like someone's eyes squeezed shut as they're laughing. :) XD

dieing laughing または like embarressed

it is laughing X=eyes D=big smile

look at it sideways it's a face laughing so hard it's dying

XD means extreme ディズニー