I just don't like people posting in topics asking questions that common sense or a little investigation would indicate they wouldn't likely get an answer. It is also related to some previous idea I had about chronological relevance - in that if the context of the topic is driven by the actions of a certain users, trying to participate in that conversation late is problematic. If anything, it is fine to post in development-related (with the addition of Community Speak) topics as long as you are adding actual content, if you are not continuing a conversation with users that aren't there, and if you aren't posting frequently into old topics.
It is mostly common sense. If someone is reading through a Zelda Coding topic and it has some information on how to do something but not enough for the user reading it, sometimes posting in an old topic like that would be fine - if the user wants to talk to those who already were in the topic then the user should check first that those people are active. In this case, information is consolidated in one topic rather than being spread out over many topics. Again though, common sense.
I forgot to mention too that some of the problem of gravedigging was handled when the upgrade to SMF 2.0 happened - some of the boards were made read-only so that they couldn't be posted in at all.