Re: [tied]

> May I ask about the reason for
> the reconstruction of the nominative marker as *-z?

Because of the rule that the thematic vowel is in the o-grade before voiced
sounds
and in the e-grade otherwise.

> Is this just my theory,
> or have you have had similar thoughts yourself?

I read it here on cybalist and found it convincing.
(Moreover, such orthography helps to clearly distinguish nominative ending
from genitive ending, plural ending and ending-less s-stem forms.)

> If it is my teaching, I will like to make it clear
> that I see no reason to posit *-z for the stage of PIE
> that we reconstruct on comparative basis,

Yes, it is the matter of the internal reconstruction rather than the
comparative one.

> I merely see a need to derive some sibilants from *-z at an earlier stage.

It is only the matter of the the thematic nominative
or are there other instances of supposed *z?

P.A.