I don't know if it's pertinent, but I've found that I experience the "error" problem only when posting a new post; editing an existing one goes through more or less smoothly, i.e. with only a several second delay.
More: Nothing had changed when I posted this.
I've taken to waiting a few seconds after hitting "Submit" and logging out/in. (...which has now stopped working, so I quit/relaunch Safari...GIANT PIA!.
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