I know what you are saying and do agree but it is impossible to steward without the help of blues in that area.
Many allow mates to come and stand with them and others allow fellow blues to mingle, whether this is to improve the atmosphere I don't know, but as i say when people cottoned on about the tickets being checked they just came down different aisles and moved across. This is obviously not helped by the lower level logistics assisting in being able to walk all around the lower concourse and stands apart from the away section.
If fans pointed out other blues then they would be moved or if the stewards ensured everybody sat down again we could find the "space invaders" but realistically I don't think it is going to happen and personally think the atmosphere would deteroriate.
One thing that i did notice which made me laugh last night was at half time was those who remained in 110/111 at half time sat in their seats whilst in 106/107 stood, which was obviously a role reversal once the second half started ;)