RFC 3977, "Network News Transfer Protocol (NNTP)", October 2006Source of RFC: nntpext (app)
Errata ID: 2037
Status: Held for Document Update
Publication Format(s) : TEXT
Reported By: Julien Élie
Date Reported: 2010-02-10
Held for Document Update by: Alexey Melnikov
Section 220.127.116.11 says:
Note that a previously valid article number MAY become invalid if the article has been removed. A previously invalid article number MAY become valid if the article has been reinstated, but this article number MUST be no less than the reported low water mark for that group.
It should say:
Note that a previously valid article number MAY cease to refer to any article if that article has been removed, in which case use of that article number (explicitly or implicitly) will cause a 423 response. A previously removed article may be reinstated (but its number MUST be no less than the reported low water mark for that group), in which case that number will once again refer to that article.
The paragraph is misusing the term "invalid article number". The wording should have been something like the corrected text, suggested by Clive Feather.