This is a great question, thank you for asking.

Roleplaying, no matter how much "in character" a mun is, is still largely an exercise on human interaction. It will be difficult to quantify chemistry, since each human interaction is unique. But naturally, amicable interactions are less stressful than abrasive ones, thus chemistry is built easier that way.

I've no particular qualifications for a writing partner, as I try to give everyone a fair chance in interaction. I'm happy to build chemistry with anyone I feel safe with—both of us should respect each other's interaction rules, and be aware not to give in to parasocial tendencies.