Even manufactured self righteousness must be addictive.
Do you have a robust academic citation for this?
None of the sources here (https://en.m.wikipedia.org/wiki/Ideological_bias_on_Wikipedi...) suggest a heavy bias, and overall it seems that bias is attenuated with stronger participation.
I haven't been able to find sources other than those linked.
Personally, I see it in articles on any topic that is controversial, particularly along the axis of the left-right divide in America. Wikipedia is a theater for activism/ideology just like every other space (like our work places) has been opted into the same war in the last 5 years or so. It is most apparent to me when I read an article about influential or popular figures who are moderate or right wing.
Also if the allegation is that wikipedia has an editorial bias, I wouldn't necessarily trust wikipedia's own evaluation of it's bias.
This reminds me of a past blog post, a few weeks ago or so, from a journalist who spoke about how strongly right leaning "journalists" often think of their writing as political influencing and counter-acting the left journalism.
I don't know how true that really is but such a tendency could be a good faith explanation for such a rule (as long as it has exceptions).