If xhtml really took off, there would just be server side linting/html tidy. Its not that hard a problem to solve. Lots of websites already do this for user gen

If xhtml really took off, there would just be server side linting/html tidy. Its not that hard a problem to solve. Lots of websites already do this for user generated html, because even if an unclosed div doesnt take down the whole thing its still ugly. The real problem is the benefits of xhtml are largely imaginary so there isn't really a motivation to do that work.