Replying to myself. A number of the accounts listed by thenextweb do have Tweets to @united visible (now?) prior to them complaining about Tweets being deleted.

Eg: complaining about Tweet being deleted: https://twitter.com/iknowimbitter/status/851640007500718081 Original(?) tweet, 7 hours prior: https://twitter.com/iknowimbitter/status/851544321564323841

Complaint: https://twitter.com/TalkIBC/status/851604796113129476 Original, 1 hour prior: https://twitter.com/TalkIBC/status/851581587967934464

Complaint: https://twitter.com/MickFerry/status/851564908915437568 Original, 6 hours prior: https://twitter.com/MickFerry/status/851474942789079040

I tend to think my theory about spam/troll filtering might be close to correct, but I look forward to finding out exactly what happened.