<<o sitelen taso e musi sewi, tan pilin pi lon insa mi.
remove e and pi lon>>
I take it that 'musi sewi' refers to some work of art or some such thing, an object, in any case, created by sitelen, so the 'e' seems right, the 'plin pi lon insa mi' v 'pilin insa mi' is a hard call, but , since PP in NP aren't yet well regulated (maybe even allowed), I have to go with the latter for now, though 'pilin pi insa mi' also works, with unknown difference of meaning.
'pona la' "Happily, fortunately"
I think 'tan seme' is a legitimate fragment; the PP in NP is always a problem, though I am getting used to it (and still want 'pi's) My question is , why 'ken sona'? It seems he does know.