I have been fairly vocal on the subject. I never minded people who commented on the pictures but the fact is that on several occasions recently it opened out to full on discussions which of course belong in separate threads. Moderators can deal with this in 2 ways, one remove particular discussions which get out of hand or just remove all posts which are without a picture. I am sure the latter is much less time consuming than the former and I much prefer how the picture threads are working now.
I don't find it much of hassle posting reactions to pictures in another thread (Quote, Cut, Open Discussion Thread, Reply, Paste, Post which is a lot less hassle than what we picture posters do) although it would be nice if there was an automatic shortcut so if you pressed quote then it would redirect to another thread but that is probably complicated and might lead to more confusion.
As I am not a poster of videos I am not sure it's my place to comment but it seems that video threads are less disrupted by discussion so I'm not sure the same strict rules need apply to them ... although once again you could end with a situation of having a couple of pages without link so maybe the need for a clean policy is nearly as great.