The membrane that separates the online world from the real world is ever more permeable. What people say online has real consequences. They may end up in prison. They may be named and shamed, and this may be enough to make them suicidal.

We don’t know and may never know what caused the death of Brenda Leyland. But Twitter does. And Twitter is certain that it happened because she was exposed as one of “the trolls” who was said to have been targeting the McCann family.

Conspiracy theories of all kinds abound, not just about the disappearance of Madeleine McCann – but now also about this tragedy.

Those who sent abusive messages about this case are seen by some to be warriors against the lies and evils of the mainstream media. Trolling, they say, is just another word for challenging.

Though social media is now so deeply embedded, we still don’t seem to have any shared social definitions of what trolling is. It continues to be seen as somehow trivial, just silly insulting nonsense that should be ignored.

But you can only regard it this way if you have never experienced it. Trolling can be an orchestrated and concerted campaign to intimidate others into silence. Multiple threats of death, rape and mutilation, as well as the publication of addresses (as much as Twitter wants to refuse this role, platforms act as publishers) is the modus operandi that brought a lot of misogyny to the surface. Trolling can also be obsessive and highly personalised – a form of stalking.

Calls for action are often tokenistic. Twitter could never employ enough moderators to look at every tweet.

The police have often been slow to act but successful prosecutions have ensued, such as that of Stella Creasy’s persecutor. Nonetheless a real unease exists over what is free speech, what is hate speech and the protection that anonymity offers.

It would be much more convenient if trolls all shared a single psychological profile, but they don’t. Some who have sent the most awful abuse appear seemingly well-adjusted in other aspects of their life. Much has been made of Mary Beard’s approach of befriending and even writing job references for some of her trolls. Laudable as this is, quite frankly it is simply too time-consuming for most people on the receiving end of pile-ons.

While there is a mute or block button on Twitter, in real life women end up installing panic buttons or going to stay at friends’ houses because they are genuinely terrified by these threats. Not that this only happens to women of course – I have had male friends who have ended up on antidepressants because of vile female stalkers.

The bigger question is whether the democratisation that social media embodies, the sense of giving all a voice, can be consistent with a tolerant and forgiving space. Anonymity is often defended as though everyone was about to overthrow an evil dictatorship, but more typically it has become the “freedom” to call someone on Question Time unshaggable.

Anonymity is the troll’s only real-life friend. It allows a disinhibition online. Combined with the fact that none of the normal feedback mechanisms of everyday life exist – no eye contact, no authority figures, no sense that behaviour is being monitored or reacted to by an actual person with feelings – all of this means people seem to think there is no going too far and there are no consequences.

Whenever there are, there is a huge yelp of rage, and that is currently being directed at the McCanns. How can they even be “trolled” if they have not seen these abusive messages, some are saying.

Trolling seems to now be viewed as an acceptable price to pay for having a voice, for the illusion of freedom. After years of social media and slightly more savvy policing, we are a long way from any consensus on how to deal with it. Ignore, prosecute, answer back, don’t feed the trolls? All of us try different strategies.

Social media reveals to us base impulses, ugly and aggressive. It merely channels what is already there. But anonymity is at the heart of this web of power. My identity is not hidden but you can choose to hide yours. This is the nature of old media versus new and one can see it played out as a kind of asymmetrical warfare. But anonymity is not of itself a noble virtue; its power can also be abused. The issue here is one of accountability. Without any sense of mutuality or accountability we create not an alternative to the mainstream media, merely an antisocial media in which the same hierarchies take hold and the same people get shouted down.