A11y is about the least accessible way of writing 'accessibility' possible. A-11-letters-Y is not enough information to go on unless you've already been primed to understand it. It's aesthetically (a11y) ugly, astonishingly (a11y) pretentious, and has just this awful whiff of artificiality (a11y) about it. In an age where machines will automatically (a11y) type entire words out for you using the shorthand is aggravatingly (a11y) lazy and unintuitive.
Quite frankly it strains acceptability (a11y). I don't think that this numeronym is being used appropriately (a11y).