Comment What I've seen from personal experience (Score 3, Informative) 237
As a long time editor I've seen how the bias works. It's frustrating because I remember when, broadly speaking, it was neutral. It starts at the top where the Wikimedia Foundation funds left wing groups and does not fund right wing groups. It runs fundraisers but people don't realize that it is swimming in money and diverting it to Art +Feminism, Black Lunch Table and Whose Knowledge.
These organizations publicly admit that they aim is to edit Wikipedia pages with leftist ideologies. Art + Feminism has an instructional guide showing how to create Wikipedia content about transgender and LGBTQ+ individuals.
Wikipedia has removed conservative news organizations as acceptable sources for news articles. The problem with that act of censorship, is that to construct a neutral article you frequently need balancing sources to achieve neutrality. Often there are facts that only a right or a left wing source will say. Given that mainstream new organizations are left wing, certain facts become impossible to source on the site.
You won't find the same treatment for conservative leaning people as you would for progressives. Often a few dog whistle words are added prominently by editors to a conservative's profile to signal that they are outside of Wikipedia's own Overton Window. And they will not uncommonly coordinate privately off-site, despite that being a violation of Wikipedia's rules.
Ironically, I remember completely different times before 2012 when I got into an edit war with conservatives that didn't want inconvenient facts mentioned about an anti-immigration organization. I spent significant time expanding a stub-like article into something comprehensive, only to be viscously attacked.
Now it's the other way round. It's progressives doing the attacking and edit warring. I was drawn to Wikipedia in part because of it's neutral point of view but it's now a progressive point of view hidden behind a few figleaf phrases here and there to deceive a superficial reader.