Props to you for actually answering my question and staying on topic
So far we have:
1. Don't mix low-speed films (RPX 25, Pan F+ 50, etc) with high-sulphite developers (Xtol, Microphen, etc)
2. Don't mix high-grain films (UltraFine 400, Arista 400, etc) with high-accutance developers (Rodinal, R09, etc)
3. Don't mix technical films (Retro 80, CMX 20, etc) with MQ developers (D-76, ID-11, etc)
Are there any other combinations that are
chemically incompatible? For right now, lets avoid the esoteric and alternative processes and stick to what you can usually find in your average camera shop