Actually, it depends.
"Uncle Jack", if that is how he is referred to, could be the entire object

subj + verb + direct obj + indirect object is one entire clause, so there's no need to split it with commas.

ie.
I ate a pie with a fork.

NOT

I ate a pie, with a fork.

so

I helped my Uncle Jack off a horse - is correct.

If you simple refer to him as "Uncle", however, and wish to give his name as extra information, you treat "Jack" as non-defining relative clause and place it in between commas.

I helped my uncle, (who is called) Jack, off a horse.

I'd suggest that difference in meaning between helping someone dismount a horse and helping some masturbate a horse simply comes from whether the 'j' in Jack is capitalised or not. (simsfreq, it should read "uncle" with a lower case letter unless you refer to your uncle as "Uncle")

Anyway, this is all beside the point. I won lunch and a beer of a colleague by proving my theory that -

people on B3TA think bad grammar is a worse crime than rape.

Cheers guys!
(Youlotfeckingsuck, Fri 28 Dec 2007, 11:55, Reply)