I’m a developer at a small startup. There is a performance review coming up for everybody. We are asked to prepare according to a list with the usual items (what are my goals etc) but also ”do you have any concerns” and other feedback. 

My main concern is a new employee (lets call this person Kim) who is still on the probationary period, but in a couple months may or may not be hired permanently. Kim has solid technical skills, but is not a team player. Kim has very strict ideas about design, frameworks and implementation, and argues loudly and incessantly until either everyone gives up or the CTO orders Kim to do it ”our” way. When the latter happens Kim interrupts meetings with arguments or statements about her dissatisfaction and brings this negativity into other contexts (workshops, brainstorming etc) effectively blocking the others from doing creative work, and causing general demoralization. 

The management has so far seemed unable to deal with this behaviour. I suspect the reason is that sometimes Kim decides to deliver, and then things get done quickly and efficiently. Maybe they hope Kim will improve socially over time. 

Problem is that I don’t see a sustainable way forward, unless Kim is is either insulated so the negativism doesn’t impact the rest of the team, or that Kim is let go when probation ends. 

Is it a good idea to raise this as a concern during the review, since they are asking for feedback? Should I raise this concern at another time? Or is it a bad idea to discuss such concerns at all?

Edit: I have 20 years prior experience as an entrepreneur, including managing subcontractors and other freelancers in small teams. For work/life balance reasons, I joined this company as an employee in a technical non-managerial role. It's a small company with relatively flat structure, one of the cofounders is handling the performance reviews. In my previous life I would have dealt with this person swiftly, but this is not my responsibility in the current role.