My opinion is that this is not a well thought out decision and one that is not really in tune with the reality of the Web3, Blockchain, or Cryptocurrency space.
Competition
One thing to see is that many blockchains are thought of as competitors to one another. Most people in the blockchain ecosystem are good people, but unfortunately it is usually the small minority of extreme individuals who make the most noise.
Placing all of these different, and often competing ecosystems into one bucket will, in my opinion, lead to a disaster. You will have people responding to individuals saying:
- "don't use X, use my platform Y instead"
- "you can't do X there, but we programmed X on our platform a year ago"
Even people downvoting en masse to new and developing blockchain communities is likely to happen.
One of the important parts of building a StackExchange community is bringing together people who are collectively trying to work together and help one another, and I am afraid that in the context of blockchain, you are basically creating a "battle royal" arena.
Technology
While it is completely reasonable for outsiders to look at blockchain and web3 technologies as all being similar, this could not be further from the truth in many ways.
Let's take a simple example:
In the blockchain world, a new "technology" has started to really pick up which is "Proof-of-Stake" (PoS). This is an alternative to "Proof-of-Work" which has had many criticisms for being wasteful of energy.
As an outsider, it can be easy to say:
"Just make a tag for [proof-of-stake]
and let those conversations happen."
But the truth is that something like PoS is completely different technologies, implementations, everything from protocol to protocol. The words "proof of stake" just mean some algorithm that uses a users funds as an economical incentive to back their activity. You can imagine that under the covers, this can be designed a million different ways. This is quite different than "Proof-of-Work", which really only has one flavor of using a hash function.
There are many more examples of where terminology means completely different things in the different contexts of these different ecosystems.
- Consensus
- Transactions
- Oracles
- Bridging
- etc...
Conversations within one giant super-community will lead to confusion to those looking for answers about a specific ecosystem, and will likely lead to poor questions and answers from that community.
For example, you can already imagine the first comment of every new post being "For which blockchain are you asking about?"
Community
It seems to me if this is the direction StackExchange is going, then it is not unreasonable to question why we have multiple communities at all?
If "tags" are the answer, why not just move all communities to StackOverflow with the appropriate tags for their needs.
I think the answer is that we know that this is not successful. That people feel at home when they are surrounded by people in their community, and engagement directly results from that.
It feels to me you are trying to solve multiple problems with this one sweeping change:
The problem of gaming the process to build a community.
We know that community proposals like Solana leave a sour taste in the mouths of the StackExchange staff. However, punishing all blockchain ecosystem projects for their behavior seems extremely unfair. It seems you already have the tooling and ability to detect when communities are gaming the process, and you should act as you did to close those proposals down. However, not all communities share this behavior.
The problem of communities dying and fading.
This looks like a WIDESPREAD issue with the entire StackExchange platform. While you have communities like Bitcoin and Ethereum which are thriving today, many other of your communities (especially those outside the blockchain space) are completely dead. I could provide a list here in this post, but I am sure you can just click the links of communities here. It seems to me you all need to define a process for cleaning up these dead sites, and then hold all communities (including blockchain communities) to those standards.
Your solution of merging all communities together to get an "aggregated amount of participation" is really missing everything about what makes StackExchange good, and is why it seems there were in the past so many different communities opened about what could be considered "related" spaces.
The lack of clarity of success of communities.
In my recent conversations with moderators and staff in StackExchange, a repeating thread I am seeing is "this is part of the old process", "this is out of date information", "these are old statistic", "these are old email templates".
It seems to me that before you start applying a heavy hand onto community development as this post suggests, you should at least publicly update how you view and treat the community development process. You cannot expect to be understood by the community when there are an endless number of completely dead "language" StackExchanges:

But now you have taken a stance to aggregate all blockchain communities.
This post, seems to highlight the bias that was placed on the Substrate community, which launched at the same time as the Proof Assistants community, and has arguably much better community engagement and statistics, however only one of these communities was threatened with closure.
Until you all express publicly the changes to policy and expectations that is clearly happening, I don't see how you can say that you are treating community development fairly.
Enforcement
Finally, a broad policy like the one outlined here is completely broken when you actually try to enforce it.
Is a community about LibP2P part of this filter?
If so, then how about BitTorrent?
If not, then how about FileCoin or IPFS, products from the same company that built LibP2P.
It feels to me the trend on the moderator and staff side has been to make huge assumptions about communities you do not know about. Instead of being stewards of community development, you have instead injected your opinions about communities you do not know about, and are applying your own opinions into how these communities should be formed. A simple example of this was the modification of the community description that happened with the Substrate proposal, as if the moderator/staff understood better than us how to describe our community.
It feels to me that there has been some kind of "management shift" that has happened in the background here at the StackExchange company, and that a lot of what made this company the GO TO place for technology communication has been lost somewhere in the sauce.
It seems to me that you all are taking simple shortcuts to solve problems that require real work, and by doing so, are affecting communities that look to this site as an outlet to build a home.
It makes me sad, but also reminds me why we are building decentralized technologies to begin with.