Modern colour LCDs are still polarised, so I can only view my phone and tablet in one orientation when wearing my polarised sunglasses. On the plus side, they make for an excellent real life ad-block to those annoying video billboards (which are just portrait LCD TVs).
I wonder how practical it would be to make a private display by removing the polarising film from it and then viewing with polarised glasses.
It's been done, pretty much how you'd expect:
You could also make something that filters all light but near infra-red so it could be seen by CCDs (on cameras or phones) but not with the human eye. Or do the reverse and flood the picture with near infra-red to prevent it being photographed.
In Japan a lot of people have "privacy" screen protectors on their cells that basically make the viewing angle very small. I always assumed it was through some form of polarization though now I'm not sure.
> The puzzling thing
I'd guess that this is because forums have forum-specific profiles, whereas mailing list are replied to from the one inbox.
Also, people can probably manage to find the signature section of a forum profile, but not their (web)mail client!
I used to own a car that had an LCD display where the orientation of the polarization was perfectly set so if I was wearing my polarized sunglasses, the screen was blank. I cut out a little overlay made out of an overhead transparency and fixed the problem.
Now-days kids could just look it up in minutes an move on. I am not sure if this is a good thing.
Many times in the past when I was looking for some cheap polarized sunglasses, I found that some were actually falsely labeled.
You can also remove the reflective sticker on the back of the black and white LCD, to make it transparent where it was previously reflective. That's how I made my calculator work with our classroom's overhead projector. (and some really interesting pranks)
BTW good work.
Note: In this case the light whose polarization is controlled is the reflected incoming ambient light, which isn't polarized; in a computer monitor it's the back light.
This article contains helpful diagrams and an obtuse but reasonable explanation: