The "Mediawiki:Excontentauthor" has a form of
content was: "$1", and the only contributor was "$2" (talk)
But if the $1 length is big enough (for example, 10K page deleting), it is truncated (as should be), and also $2 is truncated (as should not be, creating something like
[[special contribu...]]
We changed in hewiki the order of the message to
the only contributor was "$2" (talk) and content was: "$1"
and it works fine now. But @Amire80 asked me to inform you about this problem. I can't see how it can be fixed, because we can't create a parser for each mediawiki message, but he is the boss, so he knows all :-).