@PotatoPudding , I didn't
.
It's a fine line IMO. If you have no intention of ever using the full name, it seems pointless to put it on the BC (other than the MN 'to have choices') but some don't look like names.
The trend now other than on here is to put the day-to-day version on the BC (e.g. Alfie, Kit, Rosie)
I can think of adults who use both versions and some who only use the diminutive,
e.g. Christopher/Chris, Jonathan/Jon, Christina/Tina, Alexandra/Alex,
and some who are Tom, Tony, Mandy, Vicky or Beth on their BC
I'd probably be a bit surprised if Pete, Dave, Liz, or Becky weren't really Peter, David, Elizabeth, Victoria and Rebecca.