Selv wrote:

>I wrote:
> >>...or maybe it was just a scribal/typographic error?
>
>Keth asked:
> >Where do you mean the eror was?
> >
> >(in cod.reg. or in Finnur?)
>
>Finnur - especially since Codex Regius and Hauksbók have the same text -
>but I like Haukur's explanation better, anyhow ;->

You like Haukur's explanation better than which explanation?
Let's look at another example that I found now, in Grímnismál:
Verse 4, lines 4-6 are in Bugge's edition

enn i Þrvðheimi
scal Þórr vera,
vnz vm rivfaz regin.

Bugge's notes here says that the Ms. R has vm, whil A has of.
Then look at verse 20:

Hvginn oc Mvninn
flivga hverian dag
iormvngrvnd yfir;
ovmc ec of Hvgin,
at hann aptr ne comiþ,
þo siámc meirr vm Mvnin.

Bugge here adds the note: "of er af den gamle Skriver selv
skrevet over Linjen i R, og Hage sat mellem ec og hvgin
hvor det skal indføies; vm A; mangler i rWU."

So that means that the original writer first forgot to
include the "of" and then added it later by writing it above
the line. But the A Ms. has "um", and in the Mss. r, W and U
there is neither "of" nor "um".

It is clear then that Finnur had to make some choices.
Let's see what he does:
4. . . .
e,n í Þrúðhe,imi
skal Þórr vesa
unz of rjúfask re,gin.

20. Huginn ok Muninn
fljúga hve,rjan dag
jo,rmungrund yfir;
óumk of Hugin,
at aptr né komit;
þó séumk me,ir of Munin.

So you see that Finnur everywhere simply puts "of"
(in the examples I found thus far, but with Haukur I assume
he does it throughout)
Also note that Finnur adds accents, introduces the hooked o's
and e's, and introduces j's. Thus I assume that Finnur has
normalized the spelling. Personally I didn't know the hooked e
was part of normalized spelling. But if Finnur uses it, I guess
it must be.

In the introduction Finnur has the following remark on the spelling
in the cod.reg.: "Der findes en mængde fejl (skrivefejl) i cod.reg.,
der hidrører fra skriveren selv..."
(many errors in the cod.reg.,... they are due to the writer)
And a few pages further down:
"Et par udgivere har i den grad afskyet al konjekturalkritik, at de
så at sige har afvist enhver ændring i den overleverte tekst, hvorfor
de har søgt at give de mest hårreisende tolkninger af af forskellige
åbenbare skrive- og andre fejl, uagted man skulle tro, at selve de
i hds. rettede fejlskrivninger kunde have ført dem på den rette vej
og til den rette erkendelse."
(some have eschewed all changes in the original Ms. text, and this
has led to some hair-raising errors of interpretation of the various
obvious errors of spelling and other errors, and this has happened
even when the Ms. themselves contain many corrections of the spelling,
which ought to have led these people onto the right path and to the
right insight.)

Best regards
Keth