Thanks for hosting this important discussion.
Following on from Davina, then.
I guess the subsequent question is:  which side of the line should be our default position?
If we don't know, should we not post?
Again just to offer a comparison, on my other forum, anything that could not be proved to be official, was not posted. I gave up arguing with one of my other groups, who post all kinds of stuff.
I know it's a grey area. But it's sometimes quite easy to differentiate between a pose and somebody looking like a rabbit caught in headlights, for instance!
Attending official functions ok?  A pic of a star's children, NOT?

besleybean wrote:

... But it's sometimes quite easy to differentiate between a pose and somebody looking like a rabbit caught in headlights, for instance!

Thanks for these words 
I'm for sure not interested in seeing such rabbits
- and no rabbit kids as well. What is the fun of it?  *shrug*

Twitter says (well, a Twitter user concluded):

a handy guide to verboten things

I hope I’m not too forward in this, as I’m not trying to speak for the entire fandom. But when I first got into Sherlock, there were some incidents regarding certain video/pics that I had to learn about piecemeal. While I never reblogged any of the images in question, I know what’s it like to be a new fan and not have the feel of the place quite yet. It can be quite embarrassing when you find that you helped spread something that you didn’t know you weren’t supposed to. There are certain photos that are currently going around Tumblr again, so from this fan’s perspective, here’s what I know (feel free to message me if I’m missing something).

PLEASE DON’T REBLOG THE FOLLOWING:

    Any photo of Martin Freeman and Amanda Abbington’s children. Amanda especially is kind enough to interact extensively with fans on social media, and when paparazzi photos of their children appeared online, fans helped get those photos taken down. Please remember that Martin and Amanda are actors/public figures, their kids are not.
    Photos from Mark Gatiss and Ian Hallard’s wedding. Both the photographer who took them and Ian have politely asked for those photos not to be circulated. They are personal photos of a private occasion.
    “Thrillerbatch,† aka photos and/or the video of Benedict Cumberbatch dancing at a friend’s wedding to Michael Jackson’s “Thriller.† That video was taken from a hacked social media account belonging to Olivia Poulet (Benedict’s ex-girlfriend). Both Benedict and Olivia have asked that it be taken down.
    Fake nudes. I was notified that someone is circulating some doctored photos of Andrew Scott. They are fake, but even so, it is still a personal violation for the actors to come across such things. (Ask yourself how you would feel if someone slapped a photo of your face onto the body of a person in a compromising position.)
    Just in general, stay away from any photos that are obviously personal and yet don’t come from an official source (like a confirmed Twitter account).

The Sherlock fandom has a good reputation for being protective of the people who make the series that we all love so much, so while the above examples have not been totally erased from the Internet (nothing ever can be), fans have been pretty good at clamping down on their distribution. We all appreciate how much contact “the creatives† maintain with fandom, but that will go away if boundaries and privacy aren’t respected. If you see someone posting any of the above, please be polite in asking them to take them down. A lot of times, things get re-distributed by new fans who are unaware that they’re doing anything wrong.

Let’s respect everyone’s privacy and have fun (and yes, otters and hedgehogs have been officially sanctioned by Benedict and Martin, so go nuts!)

^ I think it's safe to say that personal would be any pictures of family members/private occasions (events that were never publicized)/pictures and videos known to be stolen. Basically, the examples in The Doctor's post. It's not about being right and wrong exactly, more so if you know for a fact that something is an invasion of a celeb's privacy, it is very disrespectful and selfish to post it. Especially when people's kids come in to play - always assume it's private.