I don't think they'd have enough replacements ready quick enough. They'd have to decide between an influx of spam from having no moderation and upset users, massive disruption from upset disruptive moderators, or stale content by freezing all submissions to the site.

If I were in their position, I would have trained for this scenario, and already prepared a way to put entire subreddits into 'read only' mode which just replays history - ie. show funny cat pictures from last year. Then any subreddit that starts talking too much about leaving for a new platform gets put in read only mode. Let people think they are still interacting - ie. people can still upvote/downvote/comment, but it's mostly/all dummy stuff.

But... I bet they haven't prepared, and will be caught off guard.

A lot of the depends on if you think the moderator role is truly impactful in a meritocratic way where better work is rewarded with higher quality communities and content V.S. a largely rote role which involves correctly implementing the community rule set.

If the former is true, the moderators aren't really "replaceable" in that way. You can fire them, but the output of your product will suffer as a result. In that interpretation the moderators are actually some of the most important customers of Reddit - they produce quality content in return for free hosting and occasional assistance.

If the latter is true then you can just fire them and it doesn't matter...but it kind of seems like no one believes that? If Reddit really thought they could fire them they probably would have just done it? I don't know what the truth is but I think the former interpretation dominates thinking.

The last time subreddits staged a coordinated strike like this, Reddit warned they would replace moderators next time. I wonder if they'll make good on their threat? I wish they would, the powermod situation on reddit is out of control. Part of the reason these coordinated strikes happen is because most top subreddits are ran by the same handful of people. It would do reddit some good to get variety among the moderators.