1. Gytha Oggasdohtor - As I noted in that earlier premature commentary
email, I find this name to be an obtrusively reference to the Pratchett
character.

Additionally, the name is not formed correctly; Old English doesn't
form genitives by adding <-s>, but rather by adding <-es> or <-n>. 
Examples from Tengvik of patronyms formed from names ending in a vowel
are:

<Adesune>, from <Ad(d)a> (p. 148)
<{AE}ffan suna>, from <{AE}ffa> (p. 148)
<Badan sunu>, from <Bada> (p. 150)
<Bannesona>, from <Ban(n)> (p. 150)
<Beressune> from <Bera> (p. 151)
<Bondan sunu>, from <Bondi> (p. 151)
<Hobbesune>, from <Hobba> (p. 157)
<Hussan sunu>, from <Hussa> (p. 158)
<Maltesune>, from <Malti> (p. 159)
<Moccesun>, from <Mocca> (p. 160)
<Odesune> from <Odo> (p. 161)

And others.  So, this should be either <Oggesdohtor> or <Oggandohtor>; 
I don't know enough about OE grammar to know which is correct.

2.  Halldórr bíldr - Lovely name!  No conflicts found.

The arms are clear of Valbjörn Flettir (reg. 04/1996 via the Middle),
"Argent, two Thor's hammers and another inverted gules," with one CD
for the number of hammers and another for their arrangement.  I'd
expect there to be a CD between a normal hammer and a Thor's hammer,
making this clear of Sandor Hackbrett (reg. 01/1987 via the West),
"Argent, two hammers in saltire vert," with a CD for the tincture and
one for type.  These were the closest I found.

3.  Julianna Woolworth - I've found only one example of the double <-nn->
spelling in our period; it occurs in my "Index of Names in the 1381 Suffolk 
Poll Tax" (http://www.ellipsis.cx/~liana/names/english/suffolk1381.html).
While this is a Latin spelling, not an English one, since she didn't
request authenticity for English, this is registerable.

5.  Marion la rousse - Nice name.  There may be a conflict with <Mairi
Rose>.  Since <Marion> is a diminutive of <Mary>, there is no difference
for the given names, and so it's a question of whether <rousse> looks
and sounds significantly different from <Rose>.  I could go either way on
this one.  <Marion Ross> (reg. 09/2003 via Atlantia) on the other hand
is a clear conflict.

6.  Niccola di Cristiano - This should be clear of Stephan of Monmouth
(reg. 10/2000 via Ansteorra), "Per pale Or and sable, a cross of Jerusalem 
counterchanged," by X.2, and of Maridonna Benvenuti (reg. 03/1998 via
Ansteorra), "(Fieldless) A cross botonny per pale sable and Or," with a 
CD for fieldlessness and one for the type of cross.  Otherwise, looks
clear!

9.  Ysabeau Tiercelin - This isn't Or, this is tenne.  Are the actual
forms any better?

Since the horse isn't also strewn with roundels, this needs to be blazoned
as "...horse rampant Or and a bordure Or semy of pommes."

-Aryanhwy, Albion