A long time ago, Shog9 deleted a popularly-linked question here. He then made another post, Why "What Stack Overflow is Not" was deleted, to explain his reasons for deleting the question referenced there. That post was bumped recently, by a user who removed outdated links to a domain that has since begun serving malware (a good edit on its own).
I think that more than a decade after the action referenced in the post was taken, the announcement has run its course of letting users on the site know why it was taken. Much of the content in the answers is no longer considered in scope for this site (being specific to Stack Overflow), and the post definitely meets the definition of the old "too localized" close reason (it's only pertaining to a specific period in time, i.e., the immediate time after the action was taken). I don't really see why it needs to be resurfaced every now and then.
An announcement as to why a question was deleted is useful for users who follow outdated links to the question (in old comments), so it's still useful to have around as a reference as to why it was deleted, but any discussion regarding its deletion is now well into the past. (The deleted question referenced in the announcement is no longer a good fit here as it's specific to Stack Overflow, ending the debate.)
In my opinion, the post should therefore be historically locked. To summarize, it's useful to have around as a reference (it has quite a few votes, views, and inbound links), but doesn't really need to be active. There's also precedent for historically locking similar announcements.
Should it be historically locked (once it and all answers have been edited to remove/change links that have since become dead or malicious)?
idownvotedbecau.se
) without explaining why that's applicable.whathaveyoutried.com
, that's of that variety, and no other external links (outside the network) in the post.