It's an issue with benefit cost ratio, in my opinion. What's the benefit? Well, I don't really know... but I know the cost of encoding a ~ is rather small, so it's one of those things that I'm willing to do without thinking about it.

Now, I admit, I've done things that aren't backwards compatable with HTTP/0.9 (because there was no concept of HTTP headers in 0.9, you're not supposed to return any headers unless the request string specifies that it's HTTP/1.0 or later) ... but as Apache chokes on that, I'd have to do all of the heavy lifting, so I don't think it's worth it.

I think I supported browsers without table support until about 1999 or so. (but that was mostly because we'd connect to a page to get modem debugging info over lynx, when we were trying to set up problem connections at the ISP I worked for at the time) In that case, the cost was insignificant (I had already been dealing with HTML backwards compatability for 4 years at that point, so it came without thinking), and the benefits were measurable (shaved minutes off our time in debugging connections).