These were blacklisted because there were apparently (WebKit) browsers that blocked submission for invalid values, but didn't make it clear the user why.
Testing with http://jsfiddle.net/hLceeL4m/2/ , Firefox 30.0 and Chromium 35.0.1916.153 seem to work fine.
Safari 7 seems to let you submit, which is not compliant, but also not a confusing UX the way the original problems were.
Safari 8 is coming out soon with Yosemite, so that and Opera should be tested.
See Also:
T72974: maxlength html form values are not used in preferences
T25769: Password fields for account creation are marked as required when they are not