mike.lifeguard+bugs wrote:

Apparently this is the result of past changes to the rename extension and/or database structure. French Wikipedia (and presumably all other wikis which had Extension:Renameuser when these changes were made) has similarly inaccurate log entries.

There are two distinct ways these logs entries are broken. The oldest is log entries like

15:18, August 2, 2005 Aya (Talk | contribs | block) has renamed Special:Renameuser to $2 ‎ (Renamed the user "Master Thief Garrett" to "Garrett")

The 2nd way is log entries like

23:09, May 3, 2007 Whiteknight (Talk | contribs | block) has renamed User:Rtc1 to $2 ‎ (Renamed the user "Rtc1" (which had 1 edits) to "Rtc")

And the current log entries look like

14:19, February 13, 2008 Whiteknight (Talk | contribs | block) has renamed User:Urbane to Reece ‎ (1,681 edits. Reason: Requested rename via email. No reason not to.)

Note that our log entries are different from current log entries for enwikipedia, for reasons unknown.
Their log entries are like

14:33, 13 February 2008 Andrevan (Talk | contribs) renamed User:Jamie25 to User:Illumi25 ‎ (1 edit. Reason: WP:CHU)

Note that the new username is linked for enwikipedia, but not for enwikibooks. I don't think this is really a bug, but it does make it difficult to tell what the log entries are supposed to look like (Are current enwikibooks log entries correct, or should they look like enwikipedia, and we have 3 different types of log entries here?)

mike.lifeguard+bugs wrote:

Also, some strange entries in Special:Ipblocklist
http://fr.wikibooks.org/w/index.php?title=Special:Utilisateurs_bloqu%C3%A9s&limit=500

See also bug 12782 for the CU log. Possibly a duplicate? I don't know enough about likely causes of these errors to say, so I'll let someone who does make that determination.

mike.lifeguard+bugs wrote:

*** This bug has been marked as a duplicate of bug 13889 ***