Who is the single most helpful person on talk.maemo.org?

IMO it has to be vi_ for asking this positive and community uplifting question in the first place.

The one who solves the most issues for stuck users?

Ah, this is more difficult and is very open ended.
As a forum community we evolve and change.
I think all the "regulars" are helpful and each have there own expertise to contribute and debate.
This all keeps the community growing.