The information
here ("as of the 8/13/2011 patch...") is current: the weight limit is 14.9 up through level 54, then 18.9 up through 59, and finally 22.9 at 60. The patch notes at the time stated that the game's UI does not correctly reflect the actual AC regarding these changes, so just because you don't seem to lose AC according to the UI does not mean you actually are not losing AC.