I think it's incredibly healthy to encourage that sort of "visitor" committers in an enterprise codebase, for a couple of reasons.
The problems of getting an existing employee up to speed with the codebase are a subset of what you need to do to get a new hire up and running. And so you really should have a decent story for this regardless.
And culturally, it's super-valuable to have a certain percentage of visitors, since it helps break down the silos, one commit at a time.
The counterpoints, of course, are that no team really wants to have to maintain a bunch of crap written by someone who's moved on after a quick stab at something, and it sorta sucks for the sustaining team if all the "rockstar feature requests" (as the GP put it so succinctly) are picked up by folks in their 20% time.
The former can be mitigated with a good model for managing incoming pull requests, in my experience. The latter is a tougher nut to crack.
The problems of getting an existing employee up to speed with the codebase are a subset of what you need to do to get a new hire up and running. And so you really should have a decent story for this regardless.
And culturally, it's super-valuable to have a certain percentage of visitors, since it helps break down the silos, one commit at a time.
The counterpoints, of course, are that no team really wants to have to maintain a bunch of crap written by someone who's moved on after a quick stab at something, and it sorta sucks for the sustaining team if all the "rockstar feature requests" (as the GP put it so succinctly) are picked up by folks in their 20% time.
The former can be mitigated with a good model for managing incoming pull requests, in my experience. The latter is a tougher nut to crack.