Here's the solution to FF 61.0.
https://stackoverflow.com/questions/51101566/unknown-rule-moz-document-for-stylish-in-firefox-61

Not working in Firefox 61.0

Does not work on FF 61.0 -- this is a real bummer for me!

I get also the error with "Unknown @ rule: @-moz-document"

This is the line: @-moz-document domain("wordpress.org") {
...
}

The style is local / custom style.
I am on macOS 10.12.6 Sierra

Is this connect to the release notes where it says Web Extensions are now running in its own process on macOS?

The strange thing is: the very same style loaded from userstyles.org runs perfectly fine still on FF 61.0 - strange.

Does not work with FF 61.0 any more.
All my Custom styles show the error:
Unknown @ rule: @-moz-document.

Hm, seems not to be problem with FF 61
It is also with FF 60.0.2
Till a view days ago, everything worked perfect (in 60.0.2).

Custom styles not working in FF 61.0

Hi, I have the error:

Unknown @ rule: @-moz-document.

In all of my custom styles.

Слепящие ночью страницы Файрфокса и Гугла, так и продолжат ослеплять. Зятемняет то-же что и другие псевдо-затемнители - не то что надо.

Long searched for such an add-on and found hereby !! I do not understand the negative reviews for this extension so far! I'm excited, great topics, especially the dark ones for the Google homepage, because I personally find ugly the default page of Google !! Big praise to the developer!

Awsome Thank Yoy soo Much guys

Love being able to fix the horrible things Google does in Calendar and Voice. Many thanks for this add-on!

Works good. Thanks.

I love it.

One of the few addons I would ever stick to my collection, ever since upgrading to Firefox Quantum 60+ has been reporting database errors. It is otherwise unusable and the troubleshoots I have attempted provided no solution.

Meanwhile, I'm relying on anti-strain droplets from my pharmacy to aid me in reducing visual stress.

Update deleted my styles and is completely broken in my older version of FF. What happened to version compatibility checking before update?

Puts items in the context menu without asking or having an option to turn it off.

great addon but its giving "don't use ID selectors" warning on styles even though they are required for styles for sites like Facebook

No funciona.