I have wanted to propose something along these lines, but a comment by rjzii stated it very well:

@GeorgeStocker In all fairness, an official SE post should just be locked from the beginning as a matter of policy. I'm not sure if the back-end supports locking the question and still allowing responses to be made.

During the time that the announcement in question was locked, it was not possible to add answers to the question, comment on it, or vote on it, even though the purpose of the lock was apparently just to protect the exact content/text of the question (as it was an official announcement and not a problem statement with scope for community improvement), rather than to prevent answers, voting, etc.

Let's create a new lock, the Official Announcement Lock (TM). This lock will prevent edits to the question, and possibly closure, but will allow all other actions - commenting, answering, adding bounties, and voting up or down. The text might look like this:

Locked as an official announcement. This is an official announcement from Stack Exchange and may not be edited by the community. If you wish to provide constructive feedback on or respond to this post, you may vote on it or post an answer. If you believe that this post needs an edit, flag the question or raise a new question on Meta.

  • 8
    I feel like the votes should be able to still happen; but edits would be stopped. Oct 4, 2019 at 15:05
  • 1
    Related: meta.stackexchange.com/q/290662/323179
    – Laurel
    Oct 4, 2019 at 15:05
  • @GeorgeStocker that's exactly what I'm proposing - that users will still be able to vote on the post even though they can't edit it. Oct 4, 2019 at 15:06
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    So just call it an edit lock, so it can be used as a tool for other cases where you'd want to lock edits but not everything else.
    – Kevin B
    Oct 4, 2019 at 15:06
  • Also related: meta.stackexchange.com/questions/334366/… ;-)
    – GhostCat
    Oct 4, 2019 at 15:09
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    If a post should be locked immediately, in other words the Meta basic features (getting answers and comments) should not be used by the community members, then what it's the point of posting it on Meta? it should not posted on Meta, the company has a blog and other stuff in place to post those things and they could add a link into the community digest (the Featured on Meta box at the right panel).
    – Rubén
    Oct 4, 2019 at 15:19
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    @Rubén I used to say that myself, but apparently the company thinks otherwise. This is a "best of both worlds" solution. Oct 4, 2019 at 15:19