What is the correct method for correcting incorrectly tagged names in pictures/stills?

I have noticed that when messages get posted about pictures which are incorrectly tagged, they tend not to be actioned.

So for example, this post asking about this picture; this post asking about this picture; or this post asking about this picture.

I do not see any way to actually do this on the relevant pages as there is no edit button, so may I ask what is the correct way to raise these and get them corrected? Not just for the ones I link to but just generally for my future understanding.

Thanks, 

bob