The apparent cause of this is a channel topic mentioning libera at all. This was the topic for the channel that affected me (with redacting of URL and channel name):

[memetic people] Logs, stats, etc: [url redacted] -- See also #redacted on irc.libera.chat

Also everyone in the #topic channel at the time of the takeover was apparently banned from both the #topic and ##topic channel it was supposedly moved to.

At this point, I am firmly of the opinion "fuck Freenode."