I am noticing that my cursor tool tips are turned off on my Rhino 5 (mac) after using my Rhino 6 Beta (mac). As far as I know I am not loosing any other settings when swapping between them.
Are you running 5.5.3?
An update was required to V5 to make the preferences play nice between V5 and V6 WIP.
I am running the most updated 5.5.3
I was able to repeat the problem:
This issue is fixed in the latest update to Rhino 5 for Mac. Thanks again for reporting this and for your patience.