The owners manuals on Sharps have always addressed the flickering line artifact that can occur in Dot Mode - This is not a fault of the TV as a newbie would suspect and think they have a flawed panel. Dot is about as close as your going to get to perfect on a 1080P panel. When this occurs it's because your viewing an HD Channel that is either cheating by sending non-HD content through the broadcast or field broadcasts that they frame which leads to over or underscan which is why you'll see the broadcaster often framing the content.
In Dot Mode the panel is FIXED NATIVE 1080P and that's all it can do but if the broadcast sends anything less you'll end up with that razor line artifact. Most often this will occur with late night rerun returns on local HD channels as they send it out as 480i or if you view a remote report on news/sports and you'll notice that they frame the content to prevent this proving that they are aware of it and that they are the source.
The artifact won't be observed on an SD channel since Dot Mode doesn't work on SD channels - it's not available in the Menu on SD Channels which is why one person may not be seeing it - switch to an HD broadcast Channel and it'll be there. Despite this issue Dot Mode is easily the best viewing mode for HD and makes viewing a 57" at 8.5' easy and immersive and even a 65" is doable withh Dot Mode and it's NEVER replicated that flickering razor line on my Blu-Ray and HD DVD or any TRUE 1080P source - never!!!I've owned three Sharps and Dot Mode is the best but understand it's the broadcaster that is the source that is not truly full HD contained within their broadcast signal that triggers it and they cover it often by framing with advertising, i.e.; GMA, ESPN, CNN and late night local SD Content fed through HD Channels (this content rarely gets any framing though and thus you get the dang flickering line as a result - you either tolerate it or use smart stretch or change the channel.