Why should tags never be deleted from the server?

Question

Reading Gerrit docs , it says:

[...] users should be really knowledgeable about git, 
for instance knowing why tags never should be removed from a server

He does not specify this statement. I do not see any problems with this, and I also can not find information about this.

So why should tags never be deleted from the server?

Answer 1

Why you shouldn’t remove the deleted tag is explained at the bottom of the http://git-scm.com/docs/git-tag , section “When you re-mark it”.

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Answer 2

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[access "refs/tags/*"]
  push = block group Anonymous Users
  create = group Project Owners
  pushTag = group Project Owners