I am perfectly convinced by your shower of evidences that velvet wasn’t completely out of fashion.
But you must admit that my prejudice was not so ill founded for, I repeat, in the adaptations I don’t remember having seen velvet. Perhaps costumers share my prejudice.

For Caroline.
Thank you for your link, I’ve found this interesting and exhilarating explanation in the same page:
‘Court fashions were often rather removed from those of the world outside; the outdated hooped dresses of the 1740s, for example, were still worn until around 1820.’