Improve validation for mf1 hEntry

From indieweb-dev chat today, I found that validating a microformats1 hEntry post (example) can show some misleading messages. In this example, the original post has a microformats2 u-syndication class. php-mf2 and others won’t parse that since the specification directs to parse for backcompat classes.

The parsers don’t indicate if the result came from backcompat or not, so IWM is reporting that no syndication links were found in the post (example). This is definitely confusing for publishers, because the suggested markup does appear in the permalink. I don’t know the best way to do this, but ideally the validator should warn if backcompat was used and explain that a mixture of microformats2 classes won’t be found.