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I opened this bug as a marker to check whether the LVM document had the same issue as the man page, but it does not. The LVM manual does not generally document the "lvconvert" command per se, summarizing the man page -- instead it documents using the lvconvert command for specific tasks and scenarios, with command sequences that were tested, but it does not include the wording from the man page that has been changed here. It also seems as if the issues that Corey noted here should be addressed by the new error messages themselves. So I'm closing this as not a bug.