ἐστιν / ἐστὶν → why no accent and what should be the monotonic accentuation?

[rnylk]

Well, it wouldn't really be paradoxical though when in context. Think of "ο άνθρωπός μου". Granted, "μου" is an one-syllable word so with the new, monotonic system, we're used to seeing such words without an accent mark. But it's just the same thing isn't it? We're just a generation or so away (or not, as the case may be) from those Greeks like my father who had to learn not to find it weird when they had to write with only one accent and no breathing marks (took him forever and a day) so it's a matter of perspective I guess.

[spiros]

"μου" is a one-syllable word not a two-syllable word.

[rnylk]

I do think I mentioned that and then explained why I, personally, find it to be a similar case. Of course that's only the way I see it and you obviously don't see the similarity. Forget I said anything then, no harm done (I hope).

[spiros]

I am not trying to find a subjective reason why yes or no, but a standard procedure (?) that is generally acceptable in such cases.

[rnylk]

But it's not a subjective reason. They are both enclitics. Enclitics behave the same way in modern and ancient Greek. We don't look at it the same way because modern Greek enclitics are one-syllable ones. And that's the only "subjective" part of my post. The way we "see" things. "Eστιν" is two syllable true and that's why to us, who didn't grow up with the polytonic system it the only one that seems strange. However it is also not a modern Greek word. Therefore it cannot but be treated according to its enclitic "nature" and not it's two-syllable "nature".
In other words: Enclitics in Greek "lose" their accent mark to the word preceding them. "Εστιν" ιs an encllitic. While modern Greek enclitics are one-syllable, "εστιν" isn't. This does not change the rules of the enclitics in modern or ancient Greek. Furthermore "εστιν" is not a modern Greek word so any possible controversy we may feel the two-syllable nature of it could cause doesn't signify anyway.