I'm absolutely in favour of dealing with the problem of tabs. I just edited one too many terribly formatted post by some poor schlub who probably never thought about indenting in their IDE in the first place, but definitely made zero effort to make the result readable on Stack Overflow.
Now, I'm always happy to help and edit something to look better, but having tabs in the original makes this incredibly frustrating. What's missing isn't necessarily automatic conversion, but a tool to help us edit such posts.
When I'm editing, I'm already prepared to cut up and rearrange the original material, so preserving original material is secondary. What I would really, really welcome is an editing tool that performs the conversion on request.
So, here's what I'd like: Add a tool button to the editor that converts tabs to spaces.
(Here is a related questionrelated question on this topic.)