Dennis wrote:

> Ferr dda h on i nd-ecna.
> > I wonder especially about the use of  (the preposition ,
> > a "from") here, which seems to introduce the compared thing.
> It is very odd.

I think that Liz' suggestion is very attractive:

it is better (to get) two things from one (= somebody) (who is) in the know.

No immediate comparison would be expressed in the this statement. The use of on could be the same as that 
discussed recently in the Scolc's Song-thread.