If my guesswork is good, the message should be documented as:
This is a log entry. Each log entry has three standard parameters:
- $1 - user who performed the action (usually linked to the user page)
- $2 - unused, or user who performed the action (to be used with GENDER)
- $3 - the affected page (usually linked)
Parameters $1 and $3 are invisible to parser functions; you cannot use any magic functions to read their value. Wiki markup is not supported in these messages.
That needs to be confimed, however. If so, adding GENDER support for $3 is not entirely trivial ;-) at least not for me.