I've noticed that the lighting on some of the letters on the keyboard is dimmer then the rest .... especially the letter "e" and "alt" .... ! I checked my mates phone and it's the same on his ... the letter e seems to be one that is the most dimmest compared to the rest and the odd few along the top are dim also ... but not as much as the e .. ! On my one it seems as though it is about to go out !!!!!!!
Are both your phones old? The letter 'e' is the most common alphabet in the English language (just make a table of all the alphabets in this post), so it stands to reason that the 'e' key dirties/wears out fastest than the rest.
Do a search on this and you'll read what others who have experienced something similar had to say about it. I think in time it won't bother you, but if it really does and you just got your phone you can always try to swap it out.
Keyboard Lighting !
