Sometimes when people mean a lot to you, you can addapt their voices in your head. I think this is the case here.


D'aaw

I thought it was interesting that John's voice in Sherlock's head was derisive and critical. John seemed comforted/intrigued, by Sherlock's. 

I was wondering about that "jealous" right there. Why, and what did it refer to?

Well observed, Susi, as always.
I find the voices Sherlock hears especially interesting. He talks to people inside his head a lot, like in TSOT where he has really long conversations that happen only in his mind. It seems that all the voices and people there are reduced to the meaning they have for Sherlock.
Look at Molly, for example, in the mind palace scene in HLV. I could imagine if the real Molly found out Sherlock was dying she would get more or less emotional, but the Molly in Sherlock's mind is totally calm and makes a survival plan based on her professional knowledge. So to Sherlock Molly is someone who stays calm in very critical situations. In his mind she's of course the representation of a calm and logical part of Sherlock himself.
Mycroft always appears as the helpful but annoying and harshly criticising big brother. It seems that Sherlock has internalised Mycroft's criticism in order to push himself to better achievements.
John's function is to help Sherlock get along with other people, and sometimes to point out very obvious and simple things that Sherlock misses because he's too focused on the details. Of course that doesn't work well if John is only in his mind, because there is no part of Sherlock's self that knows how to be polite to others, and he can hardly point out things to himself that he has overlooked. John has to be there in person to do that.
Another thing Sherlock can't provide for himself is kindness and affection. The voices he hears and the people he sees in his mind as impersonations of his own thoughts are never very nice to him. This becomes especially obvious in the scene in TEH where John's voice isn't even trying to be helpful but only speaks in a mocking tone, and Sherlock seems very upset. To provide the usual mixture of friendly mockery and praise the real John would have to be present, because on his own Sherlock can't find so many nice words for himself.

SusiGo wrote:

RavenMorganLeigh wrote:

I thought it was interesting that John's voice in Sherlock's head was derisive and critical. John seemed comforted/intrigued, by Sherlock's. 

Think of the situation in which this happens. It is the day after John has attacked Sherlock three times. He headbutted him when Sherlock asked him to come on a case with him. Despite of Mary's assurances Sherlock has reason to assume that John will not work with him again. And does not want to resume their friendship which might be even worse. Therefore I think he concentrates on John's negative comments/attitude. He may well think that he has lost John and knows only too well that Molly cannot replace him.

This is interesting; Sherlock has had two dangerous years taking down a worldwide criminal network, a thoroughly nasty time being beaten up by a Serbian interrogator, and returns to England to spend his evening being beaten up by John. Viewed in that light one can certainly see why John's voice would be derisive and critical.

SusiGo wrote:

As for the jealousy - this is really interesting because John has been jealous in the past (Irene) and Sherlock may have been jealous of John's girlfriends but John has never said this to Sherlock.
Maybe he thinks John would call him jealous of Molly because she adapts quite well to the task and sort of surges ahead with the investigationof the skeleton but this does not really make sense. 
Or he thinks John might call him jealous of Mary because she has become the centre of John's life, a place Sherlock previously occupied.

I think the jealousy question is one which Sherlock is asking about himself; he has gone away to fight an undeclared war against Moriarty's associates and when he gets back he has, apparently,  been replaced. Sherlock is not the first returning warrior to experience that...

 

Facinating fact about the Romans.  Had never heard that.

It is, indeed, a beautiful explanation but there is considerable doubt as to whether the slave whispering over and over again 'Remember you are mortal' actually happened. Mary Beard's book on Roman triumphs notes that there's not much in the way of contemporaneous evidence to support it, though I have wondered whether the decision by Roman Emperors to become gods may have been influenced by this. I have always rather liked the story of Vespasian commenting that he appeared to be turning into a god, as his ironic way of acknowledging that he was dying...

I see this completly different I think it shows that Sherlock is missing John and his sarcastic remarks.  Crime solving with Molly just isnt the same. And he isnt off his game, he realises its a fake crime.

I agree Sherlock is in a muddle there, after all this is the second time he is stumbling over his words (the first time was when Irene confused him).

But for me the difference is that Sherlock is missing John and not hurt by derisive remarks. What Sherlock imagnes John would be saying is pretty sarcastic but after all John has always been pretty saracstic and didnt mean his remarks to be hurtful. And I never thought Sherlock was hurt by Johns remarks. For me this scene shows how much Sherlock misses and needs John.