In my view there is no coherent, cohesive thing we can point to and call 'free speech'. The traditional libertarian approach—speech is free unless violently interfered with (whether by the state or others)—is inadequate. You don't feel free to speak if you are going to be shouted down or subject to torrents of abuse, even if none of this is physical. You don't even feel free to speak if you will be hated or even just less well liked. You wouldn't feel free to say something if your friends were going to stop inviting you out or if your firm would stop employing you.
On the one hand, this just means that freedom of speech conflicts with your employer's freedom to hire who they like, or your friends' freedom of association, or people's basic freedom to like who they want.
But it also conflicts with freedom of speech itself. Stopping me from saying my true views about what you say may make you more free to speak but it is itself an interference in my freedom of speech.
I think that no society has or could have complete freedom of speech, you can only choose to protect certain kinds of speech. For example, patterns of speech we (i.e. our laws and courts) decide count as threats, incitement, harassment, abuse, hate speech, and so on, are not permitted in the UK.
And we do permit lots of other actions by the public at large that limit people's perceived freedom of speech: for example we allow people to be rude or mean on Twitter, we allow friends to tell their friends they respect them less when they've said things they don't like.
Our society might have made the right choices: in practice this means stuff like racist speech is forbidden, homophobic and sexist speech is becoming forbidden, as well as all the obviously unpleasant harassment and abuse mentioned above.
By contrast older versions of our society allowed racist speech but effectively banned blasphemy, whether through the law or polite society. They also banned public allusions to homosexuality, graphic sex and whatnot. On our modern values, these older prohibitions seem silly whereas current prohibitions stop genuinely dangerous speech.
People take a 'thick' view of freedom of speech when their position is weak. They tend to think that violence isn't the only thing that can restrict speech—losing a job or friends can too. But when they are strong they often resort to the 'thin' account, like xkcd 1357. I don't think this self-serving tendency is deliberate, but it's easy to come to when there is no single hard-to-challenge conception at the heart of the free speech idea.
It's fine to say that the words 'free speech' just mean some or other conception, e.g. the libertarian conception. If so, I don't think the concept 'free speech' is useful as a way of thinking about experienced freedom in speech. I'm happy to use another word or phrase to talk about the concept we should care about, i.e. feeling and being able to say important things.
But there is no conception that captures all of our intuitions about things we are and aren't free to say; leaving us all free to say absolutely everything we want. In the end all societies can only choose to protect some speech, while necessarily banning others—whether through the law or social pressure—to achieve that goal.