The roads I take...

I've just read an interesting blog post about rewrites in MailNews, which would improve both Thunderbird and SeaMonkey by replacing very long-lived, historically grown, patched and hacked interfaces in the mail and news code by interfaces that cleanly apply to present architecture and are again open for relatively clean additions in the future. This doesn't mean the current code was that bad at the time it was created, it was made for the state of mailnews in those times, and those times being almost 10 years ago (early Mozilla code) or even before (code we inherited from Netscape) clearly explains why things like message tags or feed account types require some sort of hacks to apply cleanly to the old code. Also message meta info being stored at folder (newsgroup) level instead of account level means that it's e.g. hard to mark cross-posted message read in multiple newsgroups. A side effect of those reworks is also that old storage formats like Mork databases and RDF datasources can be replaced by more modern backends like the SQLite-backed mozStorage mechanism.

Joshua Cranmer, who wrote the blog post I cited above, is currently trying to get a picture of where we want to end up with such rewrites, how we can get rid of Mork ("kill-mork" work) and many RDF usages ("kill-RDF" work), and how to design interfaces in a way that they are fit for future enhancements.
When the picture gets clearer, he intends to work on kill-mork tasks in address book first, from what I read.

I am looking forward to seeing this work evolve, I think it could improve some of the code areas that many people are unwilling to touch because of their historically grown clumsiness - and in open source, it's always bad if people refrain to touch code because they don't fully understand it.