The review below mine made by @riversiderepeat says is true to an extent -- Stylish is indeed a spyware, but Stylus IS NOT. They (the user that made the comment) clearly put 0 (as in none) effort into researching the add-on, looking at the source code, reading the wiki page, or really just looking at forum posts and/or articles all over the web about Stylus and why it exists -- which is very ignorant on their end.
What Stylish is doing here is very malicious and to see it being brought back to AMO is a disgrace. Mozilla, is this the way you fight for the privacy of your users -- by letting some 3rd party companies steal the data of your users?
By bringing back the add-on to the AMO with all the spyware inside of it, which is just one single click away and people get NO warnings about the seriousness of the data they're going to be giving out for a feature that's used once in a while and never again, is seriously disappointing. Sigh.
To Stylish developers, shame on you guys and congratulations on destroying one of the most amazing add-ons that were ever created as well as the USo, the forum, and everything in between. The add-on became a disappointment once it was sold out the first, and especially even more so when it got sold the second time.