This is a slightly edited version:
For me, morning pages are the place where I am completely free to bleed on the page (à la Hemingway.) They are the place where it is safe to let everything come out. No one will see it unless you show them so there is total freedom to explore anything that comes to mind or, as is so often the case, anything that lies deeper that you didn't even know about which gushes forth once you have opened a vein.
Dorothea Brande said they should be written "in the twilight zone between sleep and the full waking state" - I think this is really so that you are not entirely in control, you are not yet guarded about what you will allow to reach the page.
Early morning writing, as Brande referred to it, is a place of feeling and emotion rather than logic or manufactured thoughts. There are no airs and graces, just a literal translation of what is on the inside.
Personally, I think they are at their best when you approach with a mixture of approaches, both Brande's and Julia Cameron's. Cameron said they are just for you, no one else should ever see them, but Brande saw them as a place for sowing the seeds of idea. They can absolutely be both. Not everything you write will be shareable, not everything you write will be any good or even make sense, but some of it can form the basis of thoughts that you can rewrite and transpose.
I have taken while sections and dumped them on the blog unedited, not always announced, but also taken ideas and reworked them until ready for sharing, until they make sense in my own mind. There are other thoughts that I would never dream of publishing as they are too personal and intimate, they are no less things that I obviously needed to address for my own benefit or sanity.
Pratik mentioned the "unrelenting pressure to be positive" on micro.blog, and I would include other online spaces, an environment and attitude that doesn't reflect life or the full gamut of emotions. This is why I prefer writing in my own space, the blog, where I am in full control and can publish whatever I want. Read it or don't, it makes no difference.
Morning pages are the next level on from that, they go far deeper into the realms of the subconscious and dredge up thoughts and feelings you would never normality admit to yourself let alone publish and share. You may filter them, sanitise or dilute them, repackage them into a form that you feel comfortable with but the pages are the place to fully explore them in their natural, raw state. This allows you to get to the bottom of them, to dive into their depths and truly understand them.
Just getting these thoughts on to the page, being able to examine them from a different perspective is a game changer: you get to look at them more rationally from a distance rather than being trapped in a ball of pure emotion within your head.
It is freeing, it is a release.