ALL bidders' IDs are disguised in some fashion in the same way as the others are in that listing (usually an a***b alias, sometimes "Private listing--bidders' identities protected" or a translation of that phrase where the seller chose to make the listing a "Private" one).
You see your own ID for the same reason you see your own face in a mirror: YOU are the one looking. Only the seller and that particular bidder/buyer (and I assume at least some eBay employees in at least some circumstances) can see the actual ID. Log out and navigate back to an uncached display of that page and you see what others see.
Note also that if you have a hidden maximum ONLY YOU can see the amount under the bid box as "Enter more than $[your hidden maximum]" since your next bid must be at least 1 cent higher than your previous bid as well as at least one bid increment over the displayed "current bid" like everyone else (or you if your maximum bid is less than an increment over the current bid or if you are logged out) who see "Enter $[current bid plus 1 increment] or more" (note slight difference in phrasing).
