I wonder of it is as bad as Reddit moderators.
For those unaware, reddit has a serious problem with "Power Mods", accounts that moderate dozens, if not hundreds, of very popular subreddits. I say "accounts" rather than "individuals" because I find it exceedingly unlikely that these accounts are run by a single person, it's physically impossible for them to have time to moderate all those boards and the ability to dictate what users of a very popular website see is too powerful to pass up. I'm sure you're not surprised to hear that the subs most effected by them are related to current events, politics, and popular billion-dollar hobbies. In the lead up to the 2016 elections some people actually started looking into power mods, trying to see if they had any connections to social engineering groups, particularly "Correct the Record", a group open about it's purpose of manipulating social media to aid the Clinton campaign. I can't recall what they found, but many people got suspended for vague violations and many removed posts. CTR dissolved and reformed under a new name shortly after. More recently, a image floated around detailing how a particular power mod had massive control over the top-50 boards and speculation was rampant about how they were likely using it for financial gain. Anyone who reposted it found their account perma'd from many of the biggest subs, effectively soft banning it. Reddit admins are complicit, as you might expect.
Wikipedia doesn't seem nearly as bad. Judging from the thread, there are definitely a decent amount of users and moderators who are nakedly partisan and actively try to control the narrative around certain subjects, however they seem much more limited in the amount of articles they're able to control. I Can't say why though. Wikipedia seems to maintain a fairly byzantine set of rules and a bizarre hierarchy, so for all I know it could contain mechanisms to prevent power modding, however selectively enforced they may be.
Personally, I'd be very surprised to see a single account controlling discussions the way they do on reddit. There are groups that certainly stand to gain from manipulating Wikipedia, but they're probably not so brazen about it.