There is not such thing as "my code". If there is, there should not be. This is the basis of collective code ownership: everybody can touch anything. Of course, we MUST make sure that our changes do not alter the existing behaviour (unless we're fixing bugs, or altering behaviour is exactly what we're after, of course).
Sentences like "if you touch my code I'll have to spend a lot of my time to correct your errors" are based on the (hopefully wrong) assumption that your fellow developers commit carelessly modified software. Collective code ownership also means collective responsibility, that should go hand in hand with the "leave your campfire better than you found it" habit.
If I touch "your" code (with which I actually mean "the code of which you were the first author") I magically become responsible for it. But be warned: this is a responsability I share with everybody else in the team. Actually I don't even have to touch "your" code to be responsible for it, as I already am. That's it. Do I see something unclear? I'll try to clarify it. Do I see obsolete comments? I delete them. Do I see comments? I'll probably delete them too, provided that the code speaks enough. If it doesn't, I'll try to make it speak. And delete the comments :-)