I'm not sure that anybody is still interested in further comments on this topic, but here are some thoughts of mine.
The Dutch roepnaam/bijnaam thing is by no means culture specific. Take English Michael or David - two of the most common male first names. I might know somebody as Dave Smith, but his "real" name might be David Smith, plus he probably has a middle name too. And Mike Fisher's "real" name might be Michael Fisher. In common English usage, Mike and Dave are nicknames (Dutch "roepnaam", although not an exact equivalent).
The confusion arises when Mike or Dave happens to have another sobriquet or epithet of some sort, perhaps based on some physical attribute (like "Goliath" for a tall person). In Dutch (my native language) you would call this a "bijnaam". What would you call it in English? Again, it's a "nickname".
I've checked 2 Dutch-English dictionaries. One translates both roepnaam and bijnaam as nickname. The other one translates bijnaam as nickname, and gives a short explanatory note (but no translation) for roepnaam.
Look at France, Germany and many other countries and you'll find the same thing. What's needed is one tag for the "Dave" type of nickname, and another one for the "Goliath" type.
