Quite.
Which is why I was a tad surprised that somehow Sherlock has to be seen to focus on the dog, rather than the person.
So I don't know if Redbeard is connected to a lost person...I think Redbeard is the one who was lost.

I was listening to an old Empire podcast interview with Mark and Steven post s3 but before TAB, and the subject of Redbeard came up, and this is what they said:

Gatiss: To be honest, I put [an explanation of Redbeard] into the first draft of episode two, and actually explained it – the reason that Sherlock was behaving like a child was because he’d once upon a time fallen for that story that your bunny rabbit has gone to live on a farm somewhere. And then we thought, ‘No, let’s hold it back because we can tease it a bit.’ And we genuinely thought, ‘We can keep this running for years.’ But then actually…

Moffat: It’s nice to have resolved it.

Gatiss: So the truth is that when he was little – and obviously Mycroft tormented him about it – is that his dog died, and he totally fell for the idea that Redbeard had gone to live in a happy valley somewhere.

Seems pretty straightforward, but then this is coming from two self-confessed liars who in the same interview very conspicuously changed the subject about The Other One when asked. And then we get another hint about Redbeard in TAB... Is it just going to be a running joke as they said, or is there something more to it... I think the latter.

Yes we do see a dog but we haven't had the explanation given to us in the show, only in interviews such as this one... I'm waiting to see what will happen I guess. The fact that it was referred to in TAB makes me think there will be more to find out in s4. I can't believe it will be as simple as the explanation given in interviews, but they're not going to tell us if it's something more than that, are they?

Actually, now that I've done some googling, I find out that they have alluded to what happened to Redbeard:

http://consulting-pathologist.tumblr.com/post/95650909132/gatiss-to-be-honest-i-put-an-explanation-of

So perhaps Bluebell was a parallel for Redbeard? And not only the mp scene in HLV (they're putting me down too), but also that Sherlock was being sent away to his death at the end, and John not realising - I hadn't connected that to Redbeard, but I'm slow to catch on sometimes

I think there might be more clues to the Other One that we haven't picked up on yet, but that's another topic...

I feel theimprobableone on John's blog might be a clue too...

It's a classic Checkov's Gun clue, if you ask me!

Why Mycroft had the name in his notebook - well, he knows what it means to Sherlock.  And possibly, Sherlock is Redbeard to Mycroft at this point (he's being sent off to his death, and he's Mycroft's pressure point).  Not sure why that would make him write the name down as code to himself, but just speculating!

Yes, just wondering why he'd need to remind himself! 

Mothonthemantel wrote:

I think in Mycrofts note book the references are to deaths that affected Sherlock , Redbeard his dog , Vernet his grandmother , the red herring as Irenes faked death and Sherlocks faked sentiment over that, and then the puzzling mathematical matrix which maybe -the other one.

Oh, I like that!

SusiGo wrote:

I just read something on tumblr which provides interesting evidence for the theory that Redbeard is not or not just a real dog but a substitute for a traumatic childhood experience, e.g. the death of the other one. Because we know how the writers love their parallels and in HoB we get this line about Henry Knight:

"Childhood trauma masked by an invented memory." 

Which would be an apt description of what might have happened with Sherlock. 

I love that idea.