Thus far, I've identified 572 questions closed with some variation on that comment over the past 2 months. The average score was 0.1, the maximum score was 19. The comment was replied to 29 times; Hopeless responded to 1 of them. These questions will need to be reviewed; Michael has started a separate discussion that will help determine the criteria which should be applied to them.
Then in early January, things started to get interesting: Hopeless started cleaning up tags. Starting with a set of web admin tags he'd identified back in September, and then moving on to a much larger group of tags. The week of January 19th he edited tags on 875 questions, closed 399, deleted 221, and locked 817; he then slowed down for a few weeks before breaking his own record during the week of February 16th with 988 tag edits, 262 closures, 546 deletions and 723 locks... and 1,513 tag merges.
The locks and merges need a bit of explanation. In the big tag burning thread, he mentions using locking as a tool to prevent bumping too many questions to the homepage:
The merges are harder to explain. Indeed, someone asked about them on February 26th, but didn't recieve any clarification. We discussed this in chat at one point, after I'd noticed the merges and complained; apparently, the idea was to get rid of the tags first by merging everything into [off-topic] and then go back through that tag and perform any necessary cleanup. It helps a bit to read this answer, in which Hopeless responds to a user complaining about a tag he was using being suddenly gone; if you think of tagging more in terms of a physical filing system rather than a folksonomy, the concern over having too many of them is understandable.
By late February, Hopeless had refined this message to its current form, and was using an app to integrate it into the moderation UI. Note that the question I just linked to is the only discussion of this I've been able to find, and concerns a newly-asked question. This becomes easier to understand upon realizing that a substantial portion of these questions were also being locked, at least temporarily - thus they would've immediately disappeared from all normal question lists, and their authors - although still notified of the comment - would be unable to respond to it.
To recap: this cleanup started with this meta post, where the only mention of closing is in answers noting that normal rules should be applied. It continued through a tumultuous tag burnination and transitioned into an effort to eradicate all mention of web admin tools from questions on the site. There was no discussion of this beyond the original tag cleanup; locking - though likely well-intentioned - obscured the scope of the effort for months. Very few others were involved in any way; a handful of people did participate in retagging, but the majority of the work - indeed, the majority of editing and moderation period - over the past three months have been the work of one solitary individual. A new off-topic reason was added via comments, without review by either the community or the rest of the mod team, and was single-handedly made into the single most-used close reason on the site, in the process avoiding both the guidance given to moderators for using off-topic reasons, and the restrictions built into the system itself for creating them: