I’m not totally sure about the chronology, but I think that the “old->new” block change on Reddit may have been due to calls from Twitter users. Most of the people I saw back on Reddit complaining about the old behavior prior to the change were saying “on Twitter, blocked users can’t respond”.

On Reddit, the site is basically split up into a series of forums, subreddits. On the Threadiverse, same idea, but the term is communities. And that’s the basic unit of moderation — that is, people set up a set of rules for how what is permitted on a given community, and most restrictions arise from that. There are Reddit sitewide restrictions (and here, instancewide), but those don’t usually play a huge rule compared to the community-level things.

So, on Twitter — and I’ve never made a Twitter account, and don’t spend much time using it, but I believe I’ve got a reasonable handle on how it works — there’s no concept of a topic-specific forum. The entire site is user-centric. Comments don’t live in forums talking about a topic; they only are associated with the text in them and with the parent comment. So if you’re on Twitter, there has to be some level of content moderation unless you want to only have sitewide restrictions. On Twitter, having a user be able to act as “moderator” for responses makes a lot more sense than on Reddit, because Twitter lacks an analog to subreddit moderators.

So Twitter users, who were accustomed to having a “block” feature, naturally found Reddit’s “block” feature, which did something different from what they were used to, to be confusing. They click “block”, and what it actually does is not what they expect — and worse, at a surface glance, the behavior is the same. They think that they’re acting as a moderator, but they’re just controlling visibility of comments to themselves. Then they have an unpleasant surprise when they realize that what they’ve been doing isn’t what they think that they’ve been doing.