@ barrister
Ah so that's what mosquito noise is. I guess it might be, although I see some artifacts that look more like the sample image you attached. I wonder if someone else has seen the exact same "issue" I'm seeing.
Mosquito noise is a common compression artifact.
It's not the TV's fault. May artifact na talaga yung video signal. Kahit DVDs, meron din pag hindi magaling ang video mastering.
Maybe the artifact on your pic was caused by the TV station's software that produces the ticker and font. I notice that the artifact is on the ticker and font, but it's not present on the videotaped picture itself.
Don't worry about artifacts on cable TV, since freeview images are so bad that artifacts are expected. Try looking for it on a commercial DVD source, at least.
As for the cross-hatch pattern, I found another pic, posted on avforums (U.K.):
On that pic, the patttern is most visible on the right side (where the wall is reflected) and at the top left (where the ceiling is reflected). http://www.avforums.com/forums/plasma-televisions/983263-panasonic-tx-p50x10-screen-reflection.html