I have not seen anything about the influence of the temperature on a paper developer. Right from my first prints I've noticed that low temperatures would slow down the process and give me very low contrast with no blacks at all. Higher temperature would not only raise the Dmax but the developing time as expected, while I have not noticed any loss of values due to contrast change.
The only paper developer I've used is Ilford Multigrade and although the company has a reference on the influence of temperature and advices on keeping it at 20C/68F there is not much detail.
So, is there any real information available or I should just keep the temperature around 20-25C as I do avoiding the extremes without worrying much about it?
I asume though that different temperature would influence the chemicals in the developer and extremes could result to uneven work, effects that can change from developer to developer.