Props @johnmaeda for this idea.
I'd expected to not see the competing Write action when I'm already writing!
It's also very close to the Update/Publish button, which can be confusing. Do I click Write when I'm done?

Found via #user-report and #reallife "wine tasting."
I like this idea.
But then again, UIs that adjust themselves magically to the current context can also come across as confusing or inconsistent.
To take it to the extreme: when someone is currently writing — that is, actually typing — we could hide everything except the text area.
Maybe an alternative is to fade the button — and maybe other things as well? — into the background a bit. Make things lighter or darker or ... something else?
In any case, I think hiding a button that is otherwise always there could be more confusing than helpful.
I like the idea of changing the button state to "Active" like when you click it, it goes grayscale or opaque a bit so it doesn't look clickable. When making the help videos recently JM commented he made a big red X through the button because people were confusing it with the publish button.
+1 to the idea of trying to do _a thing_ to the button rather than hiding it for the same reasons Leif is suggesting.
I like the idea of changing the button state to "Active" like when you click it, it goes grayscale or opaque a bit so it doesn't look clickable.
This is actually the intention behind the current design — the dark blue is the calypso masterbar's active state.

people were confusing it with the publish button
That seems like the root problem. And the Masterbar's dark-blue active state isn't helping.
We could try fading the button, but its not great:

Hiding the button is weird, but it does help keep the emphasis on the Publish/Update button:

We could replace the button with some other useful link or information, like drafts or saved status:

Its also worth considering how this affects things on mobile. Removing the write button is going to look strange:



We could also ditch the masterbar when writing.
We could also ditch the masterbar when writing.
I love that.
This was fixed in https://github.com/Automattic/wp-calypso/pull/20326.
Most helpful comment
I like the idea of changing the button state to "Active" like when you click it, it goes grayscale or opaque a bit so it doesn't look clickable. When making the help videos recently JM commented he made a big red X through the button because people were confusing it with the publish button.