What's made me focus on this is getting my 11 yo DD her first phone and we're going to have to say yes to WhatsApp as that's what all her year will be using to meet up etc 
My particular bugbears with it are fact that she will be joined into massive group chats even if we/she doesn't want to be & it's difficult enough as an adult to opt out of them w/out looking anti-social/passive aggressive 'Soandso has left' let alone an 11yo wanting to make new friends!
Also fact that her number will be visible on these group chats outside her contacts. Can someone explain how it is I can see who others are in group chats who haven't signed their name & aren't in my list of contacts? Is there any way to change that for our DD and me for that matter?
I want to start a campaign to pressure FB/WA to change these things (Insta have just done a couple of good modifications recently). In the interests of research have you had any bad experiences with either of the above &/or are there other major things you'd like WA to change? Lastly is there a better thread I should move this to I'm a MN newbie, TIA 