And now for something completely different...

[Geoff Bannister]

No: HPFGUIDX 137871

--- In HPforGrownups at yahoogroups.com, "docmara1" <docmara at c...> wrote:
> > Ersatz Harry:
> > Quite the opposite, I think.  If the cut is on the back of his 
> > right hand, then he presumably wrote it there with his left.  
> > Magic or no, it would be a rare person who could use his writing 
> > hand to write on that same hand's back.

Mara:
> Don't have the book at hand, but what I recall is that *at the same 
> time* as Harry was writing on the parchment, his writing hand was 
> bleeding -- the blood from his hand supplied the "ink" for the 
quill.  
> All of this with his right hand.

Geoff:
Two points.

Firstly, re Ersatz Harry's comment. He didn't write on his hand. That 
was Umbridge's magic. So I don't see that that suggestion is relevant.

Secondly, I don't think that canon specifies which hand.

'Harry raised the sharp, black quill, then realised what was missing.
"You haven't given me any ink," he said.
"Oh, you won't need ink," said Professor Umbridge with the merest 
suggestion of a laugh in her voice.
Harry placed the point of the quill on the paper and wrote: I must 
not tell lies.
He let out a gasp of pain. The words had appeared on the parchment in 
what appeared to be shining red ink. At the same time, the words had 
appeared on the back of Harry's right hand cut into his skin as 
though traced there by a scalpel - yet even as he stared at the 
shining cut, the skin healed over again, leaving the palce where it 
had been slightly redder than before but quite smooth.'

(OOTP "Detention with Dolores" p.240 UK edition)

There does not seem to be any specific reference as to which hand 
Harry is using to write.