Surprised to see so much negative feedback. I agree that clear responsibility is important, and that adding multiple assignees when those people share similar responsibilities could lead to the bystander effect.

I'm really excited about this feature. I feel like "If only GitHub Issues allowed multiple assignees" comes up in conversations with colleagues at least a couple times a month.

For context, the design (and development) team I work with uses GitHub Issues religiously. Right now all issues that need design work are explicitly assigned to a designer, and we use a label based workflow combined with Codetree to help organize weekly sprints. Having multiple assignees will allow us to explicitly assign a product manager to each of these issues w/o having to take it out of each designer's sprint, which will help make sure all design tasks receive feedback and move forward in a timely manner.