Could somebody confirm this?

If you use extended field location, it should be displayed inside
{USERCOMBO}

this way:
$ue = $tp->parseTemplate("{USER_EXTENDED=location.text_value}", true);

it return empty value. string(0) ""

It could be used directly in template too:
{USER_EXTENDED=location.text_value}

In news EUF is used this way:
e107::getParser()->parseTemplate("{USER_EXTENDED={$field}.{$type}.{$userid}}");

so I think this should be fixed in forum plugin