So we have just spotted something. We are using articles on our homepage and having the article use the forum for discussion (creates forum posts automatically) however an issue we have spotted is when we lock a thread, it doesn't lock the comments on the article and thus allows users to keep posting and also updating the closed thread.

This is a MUST in needed functionality.

You should be able to to do this. Have you enabled the fields in the database. Once done you can set them how you want.

"Hello,
There is no way in which to do that at the present time unfortunately, and its the first time I have seen it mentioned so it may be worth posting that up as a suggestion in the product feedback section of the community forums.
Kind Regards,

Marc Stridgen
Invision Power Services, Inc."

You can do this if you lock both individually.

If you want one to lock the other the Rules app may be able to help.

However yes it should be linked. When you delete one you have the choice to have it also delete the other in the settings, so locking could be there too.