ok so imagine you are having a lot fun and chit chat with someone and he/she suddenly says, i thought you are a mature person but I was wrong, you are multiple times an immature person.
Can someone even pass this type of remarks and judge you in your funny/jolly mood? What would be your feelings after listening that? It hurts
Re: Difference b/w having fun and immaturity
fun is pleasant feeling, while immaturity is childish behavior.
It depends, who is saying. 
Re: Difference b/w having fun and immaturity
he/she is stuck up douchebag/douchbagess
Re: Difference b/w having fun and immaturity
So according to this person........someone who is mature can't have fun??
Maybe he/she didn't actually mean 'immature', people say things they don't actually mean all of the time. Especially when they are in a good mood...some get a bit carried away. In his/her mind fun might = immature and serious/boring= mature........
I personally wouldn't hurt me so much though.
Cheer up!
Difference b/w having fun and immaturity
I don't understand, on what basis did they say these things? Was something said? It sounds pretty silly to me, and it sounds like that person may lack some maturity him/her self.