I have set up a (numerical) Custom Profile Field, which is an optional field for the user. If the user does not fill the field in, I hoped it wouldn't display on the topic pages. I posed the question on the BB3 support forums, and have been advised that it is a bug and that I should report it here, so...
The custom field has the following settings:

Load Settings, 'Display custom profile fields on topic pages:' = set to "Yes"
Custom Profile Fields, 'Show field if no value was selected:' = un-ticked (so a "no")
The Default Value field is blank.
The field is blank within the UCP (where the user hasn't filled the field in).

Despite the setting above to not show if no value is selected, it does show, with a value of '0', see screenshot attached.

I'm using version 3.0.12, style Subsilver2