Field restrictions in freePBX

I frequently find freePBX not allowing certain characters in fields, such as ‘_’ etc. – although it seems valid to have/use these characters in asterisk. Are the restrictions necessary?

Also, I have some users (family members) who really don’t want to have to enter a password for voicemail but freePBX forces the completion of a password and I have to remove it manually after - any way around this?