If 'Constant Seeding' option is checked, and later unchecked the torrent does not revert back but stays as 'constant'

That is because when you click constant the upload limit is removed. Just reset the upload ratio and the torrent will stop when it is reached.

Constant Seeding
Normally, seeding transfers will be paused by the system (standby queued) when the 'Upload Slots' setting has been exceeded. Transfers that are set to 'Constant Seeding' will never be paused by the system and do not consume upload slots.

This is not related to ratios. It merely bypasses the limit set for upload slots.

http://support.tixati.com/Transfer_Properties_-_Options

You need to re read their question. He/she is saying that when they uncheck constant seeding that the torrent remains constant. Since we know this does not happen the torrent will come out of constant and go to normal we have to guess what he/she is referring to. My guess is they notice the lack of time to finish or the lack of ???. That has everything to do with ratio!!!