If you want to be identified ( by Names ) , you need to configure accordingly when you first downloaded ( or subsequently alter ) “WhatsApp” into you Handphone or computer. This is the same as when you set up your desk top/laptop- you are asked to name your device. When you named your computer and connected to Networks ( WiFi,etc ) your computer name will appear in the Networks Gateway.
If no name is given ….the Networks Gateway will display a series of MCA/ISA or Pos number XXXXXXXXXXXXX ( could be as long as 32 number and alphabets. This is the same as WhatsApp – a named device when joins a Chat will automatically let the Chat Room/Group know who and who are on line.
I will quote some examples of members who I never ask for their phone numbers but I can identify by their names even though I had never meet them- Daisy Yeo;Richard Wong, Sharon,Anne Chee, aaronLow,Chiang ChengpunI, Freeda, Josephine, Richard Le Chang. All mentioned names are not registered in my devices contact list. Any one can inspect my device to verify.
So, if you join a Network( Chats,Skype,etc,) a named device will facilitate you identity, otherwise be courteous to provide when ask politely.
Note: MCA = Micro Channel architecture;POS=Programmable Option Select