I define "proper" as one that "correctly" and ideally uniquely represents a user for a given scope of work. Refer to how to configure a git identity.
Motivation: I have a colleague that seems to think its a "trivial", "non-issue" to use multiple identities; often one or more per machine from where he is working (i.e. noobie <noob@mylaptop.com>, nb <NooB@mypc.com>, boob <not.even.close> etc.). I haven't been able to convince him to clean up is act.
I'm looking for convincing 3rd party explanations of the pros / cons of using a correctly representative identity. Links to articles, manuals, docs, etc. welcome. Stick to factual pros / cons, no opinions please.