I signed up for WikiTree November on Nov. 4,2018. By its own count, I made more than 6,000 contributions & earned dozens of badges. Then, after a spat on their G2G forum, in which I was accused of fraud and spamming for posting links to tartan background images I created, based on the official threadcounts for the Swedish & Norwegian Tartans, I found my replies in my defense hidden; then I was unable to answer questions on the forum, or send Private Messages, or edit my own Profile, or Profiles I'd created for my relatives.
I had a horrible experience with WikiTree and got nowhere in learning about my family. The website is run by people who control your every move. My entries were merged with others' without my permission and some were removed for capricious reasons. I honestly felt harassed. After a couple of years, I gave up completely after receiving a really nasty message from another user. I then tried to delete my account--and they wouldn't let me! Some mystery person who apparently was one of the site controllers/admins kept messaging me about how I'd "made too may contributions" to leave. I was told that the only thing I could do was request anonymization of my data, but I couldn't leave. That completely freaked me out. I was unsuccessful in getting my account deleted. WikiTree is both a cult and a scam; they build their site on the backs of contributors and then refuse to do what the contributors want._____________
Update 5/19/2023: Now that a year and a half has passed since I wrote this, I'd like to make a comment about the five-star reviews that have appeared since. Interesting, isn't it, that they sound like some sort of ads that reassure people that WikiTree is helpful and not abusive and creepy. Also interesting is that two of them were written one week apart in October 2022. Clearly someone is behind a campaign to "rescue" this horrible website from the (very accurate) 1-star reviews. Take that into consideration as you read.
Answer: Wikitree is free, and your pedigree doesn't seem to get changed by other users as often as babies' diapers like it does on FamilySearch.org, the only other free, genealogy site I use regularly.
Answer: I've been blocked from posting in their forum, or sending Private Messages. The error messages offer an email address info@wikitree.com, but I've never tried it. The normal avenues for requesting help are their G2G Forum and Private Messages to Leaders and Managers. And this is kind of irrelevant, because no website which encourages you to create a personal profile should ever prevent you from editing or deleting it at your discretion.
WikiTree has a rating of 1.6 stars from 22 reviews, indicating that most customers are generally dissatisfied with their purchases. WikiTree ranks 48th among Genealogy sites.