Topic: How are you using Basecamp? / Moving 'to-do' lists to different projects

I think we can not do that with basecamp, Grazi :-(

Topic: How are you using Basecamp? / Moving 'to-do' lists to different projects

Use to-do list templates.

Topic: Troubleshooting and Bug Reports / Missing Messages in Categories

You put like that:
...projects/2093489/msg/cat/archive

to view all messages in one category.

Topic: Feature Requests / Multiple Categories

I think so, it is useful.

Topic: Miscellaneous / Strategic Partner Program

Vietnam office ready and waiting here, too :-) !

Topic: Feature Requests / Messages formatting guide

http://hobix.com/textile/quick.html#external-references

Topic: Miscellaneous / Short URLs for Messages, To-Dos, Files, and Milestones?

It’s ease: please this format
I searched Google

Topic: How are you using Basecamp? / Multiple responsibilities

I think it is easy. You creat a USER as your team/group and assign.