Hi Joy and Erica, wow, thanks for all the info!
Yes, I have seen this straight holder-away-from-the-body position you describe in old books … On the other hand I also saw the example with John DeCollibus (stunning

) - and Barabara Calzolari does her bird-and-feather flourishing also with an oblique holder.
Do you know the earlier artwork with off-hand flourishing like from van den Velde or here from Balderick van den Horick from around 1630:
http://bibliodyssey.blogspot.de/2009/03/quill-and-flourish.html?
These dutch penmen for sure were flourishing with a straight, very pointed, but still broad edged quill. So my impression is that there is not THE perfect tool for one thing.
And all these beautiful artworks, from past or present, are all the more reason for me to believe that the motivation to use or not to use an oblique holder is more a question of personal taste and / or tradition then that there are really "rational" reasons. In the sense that what a writing person gains from the one holder she loses when using the other (ease of shading downstrokes vs. other shaded strokes), and so it comes down to just what somehow appeals more to someone, in her / his personal style or workflow.
I feel what I want to say is a bit complicated and so I hope it is not totally obscure

Anyway, I will look for the other video - sound interesting! (What I find somehow frustrating with these videos is that they often don't really focus on the actual writing … I am aware that it is not easy to film this though.)
Erica, you anticipated some of the things I wanted to say

- I like that quote from Alan Ariail very much!
I also think that an oblique holder makes learning scripts like Spencerian or Copperplate, easIER, like you said, Joy - it is hard enough to get all the rest right.
For me it was a revelation when I tried an elbow nib for the first time! I had tried around before with a straight holder (and nib), and of course the problems to get started are even bigger.
Erica, I think in Europe many, many people simply don't know that something like the oblique holder exists. I think there is only the simple plastic Speedball to buy here. I don't know about these starter ses, but maybe it has also to do with profit …? I mean, even the most inexpensive oblique holder costs more than a simple straight one.
Also a lot of modern / contemporary calligraphy I see on the internet is quite upright, so maybe ok-ish to make with a straight holder. I use one simple pointed pen script that I developed out of my handwriting (before I started with formal scripts) that I still like to write with a straight holder because it is not so slanted, + in this case I like the irregular lines.
As you can see, I very much like to dive in the history of something I am trying to learn … so what I also found interesting is what Joy said about England and the broad edge tradition. It is similar in Germany. The books by Edward Johnston (who was not overly fond of pointed pen scripts) were translated to German in the early 20th century and are still a heavy influence, as far as I can tell. In my german calligraphy books pointed pen scripts are more treated like "Oh yes, there are pointed pen scripts, but they are difficult to learn and overly ornate!" (I exaggerate maybe a little. Great books otherwise!).
But I am totally with you - I am also absolutely pro oblique holder. I just find the history of the use of different writing instruments fascinating and like to learn more. What I find a bit sad is that this seems to get a bit ideological with some … I mean nobody is forced to use an oblique holder …