We recently updated to 1.23wmf13 from 1.16 and have noticed that tables with the class of 'sortable' do sort, but no longer persist if a visitor leaves the page and returns. I have built a table as described below and used the advice found here. This worked in the old version but does not in 1.23.
Everything seems correct, but there are no errors in the console and nothing changes in the cookie when a table is sorted. My only thought is that there is a change to MediaWiki in between versions that nullifies this bit of js.
{| class="wikitable sortable" id="testTable"
|-
! Fruit !! Price
|-
| Apples || £0.95
|-
| Oranges || £0.85
|-
| Pears || £1.15
|}