My view, for anyone who isn’t following the bug: the “undetectable” part removes some of the major objections in “Proprietary Features Bad” but still, the negative part of the message this sends out outweighs any evidence I’ve seen of a technical benefit. Even bclary, Tech Evangelist extraordinaire, admits that it doesn’t make all that many document.all-using sites he’s looked at work.
But, if we must have it based on an argument of “legacy pages that no-one is around to update”, we should have it only in quirks mode, and not in standards mode. Other compromises we’ve had to make in the past notwithstanding, we should do our best to support only standards in standards mode, and keep backwards-compatibility behaviour restricted to quirks mode. This would also have the significant advantage of making it much less likely that anyone would code new pages using document.all.
Followup to the DOM newsgroup.