I’m sure you’re aware of the discussions that went on that disabled javascript access for emails in Thunderbird 3, even if users wanted to override that. As I understand the logic, it was that 1) javascript exploits occur on a regular basis, and need to be fixed in security updates. 2) email is too efficient of a method to distribute such exploits. 3) the vast majority of users that would enable javascript really don’t understand the risks involved.

That is clearly a decision about the target audience of Thunderbird. That is, Thunderbird is targeted to be a basic email application targeting the masses, rather than an engine of innovation targeting sophisticated users. Or perhaps it is a decision that caters to a philosophy that people must be protected from their own stupidity, rather than a freedom at all costs philosophy. Regardless, I had nothing to do with those discussions, and they don’t really have much to do with filters.

I would hope that the decision about javascript would be reconsided at intervals, but with the current aversion to controversial discussions, I doubt that will happen in the foreseeable future.