Xenforo [OzzModz] Old Thread Warning will show a warning to users if a thread has not received a reply in a certain amount of days which is defined in the addon settings. You can also exclude the warning from showing on threads in certain forums. There is also usergroup permissions so you can disable the warning for certain usergroups.
You can also choose to disable the “Post reply” button until the user checks a checkbox acknowledging that they know the thread is old and want to reply anyway. This is on by default.
There are five different type of warning block styles to choose from. The five types are, highlight, important. success, warning and error.