Did the person who thought it's great idea to use grey for background colour as indication notecard cannot be modified... actually try to _read_ anything rendered in such manner?
Dark grey text on grey background is terrible. Bordering on unreadable on correctly calibrated monitor at worst, and at best makes one continually squint.
There is huge, bright red padlock icon in the corner of the window that stands out pretty well. More than enough of indication that no, one cannot modify the notecard. Or if you *really* need to make it more clear then pop up a message "this is no modify card" or something when one presses the key with card in focus, or something... but don't make things hard to read just because grey = read only with some interface elements... or at least make it lighter shade of grey so there's more contrast with text :<
(and please fix the Properties window while at it, it suffers from the same issue -- too dark grey shade of background makes the slightly more grey text nearly unreadable on Properties window for (no modify) items)