This is a functionality change. In iOS 11, Apple disabled some OS level functionality we used to swipe on a cell and then continue that motion to swipe between posts. So we had to disable one or those to make it work again.
We chose to disable the swipe on a cell to vote as the default behavior so that swiping between posts would work. In this mode, you can long-press to bring up the voting panel.
You can change this default in Settings->Enable Swipe in Comment Cell, but with this setting active, you can only swipe to vote and not swipe between posts.
We are working on updated user experience to work around the OS changes and hope to have this implemented in the near future.