Is there any character like that?

[Koen G]

I remember Takahashi writing that sometimes he doubted whether there was a difference between o and a at all (in certain contexts?).

Anyway, these kind of illustrate my point. There is a clear difference in context between EVA o and a. These contexts roughly correspond to one of the two forms. So even when many utterances are imperfect, we still end up assigning them to different characters.

Without such discerning contexts, there's only the madness of the continuum.