Jesper, with regard to you or anyone else wanting to adjust your phpBB board so that this profile field accepts both local and international user names:
If you go into the ACP, Users and Groups, Custom Profile Fields, and from there edit the current "phpbb_googleplus" profile field settings. Down at the bottom of the settings page (further down, below even the "Save" button) there is a "Profile type-specific options" button. Here you can actually change the validation that is being requested for the Google+ type field. Switching from the current "Alphanumeric only" to "Any letters, numbers and underscores" should be the equivalent to the current setting but "international-friendly".
(The regular expression used for evaluation switches to
. "Alphanumeric" is indeed just A-Z, a-z and 0-9 plus underscores as described. But the "any character" expression permits matching any Unicode character in the category "letter". "Letter" as opposed to symbols, marks, etc. And so this includes "letters" used in languages other than those that could be represented with alphanumeric.)
Yes, based on what Google+ documentation shows, the regular expression set by default for field validation on this profile field is too restrictive, and/or was only correct during some earlier feature level of the service. The phpBB profile field handling allows entry of either your Google+ account ID number (numeric only), or of your Google+ custom profile URL (which is when phpBB's Google+ string type prefixes "+" on the non-numeric-only data you entered). But the Google+ custom URL is allowed to contain characters that phpBB isn't going to let you enter under the default field validation.
The same may or may not be true for the other fields which have an entry validation set by default. It will depend on knowing the specifics of each individual service, and how they handle usernames, user IDs, and international characters.
For example with Facebook, originally Facebook does handle it the way phpBB is expecting. For example your name might be "Jesper Møller", but the Facebook account name and page are https://www.facebook.com/jesper.moller.927
which is what is needed for & passes the phpBB default profile field validation. But Facebook also has user pages (or more specifically, now
they do) in the form of facebook.com/people/Jesper-Møller/1278139731
. i.e. Real name, but with additional identifying disambiguation number. Which phpBB isn't supporting and wouldn't be allowing the needed character entry for.