Yes, that is the correct interpretation of the braces. There are authors who have affirmed the CA, but who never signed up to LDraw.org, so don't have UserNames. The header checker on LDraw.org uses the braces to know what list to validate against. There are a couple of special cases - {LEGO Universe Team} and {LEGO Digital Designer}.
Nothing forbids Steffen's suggested tabular padding of the !HISTORY lines, but when I have needed to admin-edit the headers I have usually removed them. The !HISTORY lines are "history", and it seems somehow wrong to change history. I don't have particularly strong feelings either way, but the un-tablulated format is what what I had in mind when I developed the header spec, even if it is not explicitly stated. I don't think I have ever seen a HOLD for badly formatted !HISTORY and would challenge it if I did.
Nothing forbids Steffen's suggested tabular padding of the !HISTORY lines, but when I have needed to admin-edit the headers I have usually removed them. The !HISTORY lines are "history", and it seems somehow wrong to change history. I don't have particularly strong feelings either way, but the un-tablulated format is what what I had in mind when I developed the header spec, even if it is not explicitly stated. I don't think I have ever seen a HOLD for badly formatted !HISTORY and would challenge it if I did.
Chris (LDraw Parts Library Admin)