Stylish collects and transmits all your browsing behavior over the internet in order to analyze and sell this data. Have a look at 'Stylus' which is a fork of stylish without the invasive privacy infringements.

https://robertheaton.com/2018/07/02/stylish-browser-extension-steals-your-internet-history/

According to this:
https://www.bleepingcomputer.com/news/software/2-million-users-impacted-by-new-data-collection-policy-in-stylish-browser-add-on/
https://robertheaton.com/2018/07/02/stylish-browser-extension-steals-your-internet-history/
https://www.ghacks.net/2017/05/16/stylus-is-a-stylish-fork-without-analytics/

this plugin tracks your internet traffic. This cannot be tolerated

According to this article the Stylish browser extension violates your privacy by sending your browser history to foreign servers

https://robertheaton.com/2018/07/02/stylish-browser-extension-steals-your-internet-history/

This cannot be tolerated and breaks trust. No more Stylish for me.

Spyware!. Records every keystroke, every website visited, and sends it to their server: https://robertheaton.com/2018/07/02/stylish-browser-extension-steals-your-internet-history/

Not working in Firefox 61.0

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

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

No funciona.

NO ME DEJA PONER NINGUN TEMA

No funciona

The owner of userstyles.org incorrectly configured his website. To protect your information from theft, Firefox did not connect to this website.

This site uses HTTP Strict Transport Security (HSTS) to indicate that Firefox should connect to it only through a secure connection. As a result, you can not add an exception for this certificate.

Firefox Quantum 59.0.3(64bit)（2018/4/30更新）にてエラーが出て使えなくなりました。
ある日突然、このようなものが出るようになりました。これが何なのか分かりません。
https://imgur.com/a/FWUlcys　直し方が分かれば教えてください。

動作が重たくなるし、設定通り正しく動かない時がある。
最も重要なのが、バックグラウンドで通信している。

It doesn't work: "Возникла ошибка доступа к базе данных Stylish"

database error!

causes high cpu usage for no reason and has questionable data collection
will move on to another plugin

This addon seemed to work on the past months but now! IT DIDN'T !! rather it gives me like a database error though... reinstalled then it's still same rip stylish... well i'm actually done and would never look again

v3 は v2 とは似ても似つかない、偽物という言葉がピッタリくる。v2 からの移行ができないだけでなく、多くの劣化点があり、使い物にならない。

・極端に重くなる（v2 では問題なかった）。
・スタイルが反映されないことが多い。
・エディタは指摘するのが大変なくらいバグだらけで、まったくの役立たず。

"An error has occurred using the Stylish database. Would you like to visit a web page with possible solutions?"
What is going on here?!!? Add on can't be opened anymore :(