Try adding a tag with the letters “fix” and iD suggests both “fixme” and “FIXME”. If this were hand-coded in iD, you’d get only “fixme”. So it’s pulling both variants from the database.
As an aside, I think db insertion of keys ought to be case-insensitive and it is justifiable running a conversion operation on existing keys. Or at least on fixme.
That’s a good idea. But there are times when it is sensible to use an undocumented value with a key. Which is where taginfo comes in useful. But you have to use it with care. A value might be rarely used but is perfectly valid and sensible, it just happens that there’s not much of it in the world. OTOH, a value might be rare because it’s not a sensible thing to use.
The usage of a tag can get extended, sometimes sensibly, sometimes not. Access may have started as access on roads, but it’s a small step to use it for parking, and not a vast step from using it for other things like swimming pools. Opening_hours originally applied to shops but now also applies to other things like buses (where “operating hours” makes more sense but we already have “opening hours”).
Access=employees is not particularly helpful, though. If I look at a pool on a map and it’s private, I know I can’t use it. If it’s public I know I can. If the pool is part of a member’s club then access=customers is meaningful. For somebody who has never been there before, there is no real distinction between access=private and access=employees. So access=employees is nice for those of us (like me) who obsess over detail, but private is adequate if you’re not obssessive. Employees don’t need it marked on the map because they’ll be told they can use it when they get the job. 
Note that if the situation demands it, you could have “access=employees; customers” but most renderers may not handle it correctly and it’s not really necessary to have those in combination except in bizarre circumstances. The least restrictive access generally implies access is also allowed to more restrictive cases.
Note also that access=public does not preclude fee=yes. There’s a pool near me which is public and charges a fee.
Thanks for checking. Such a simple thing to do, but you’re the only one (of over 100 people who have seen my posts mentioning the problem) that has done so. Since I’ve checked with two computers using different operating systems and browsers, either I’m doing something very stupid or there’s something blocking the routeing between me and a particular server that pushes out a critical chunk of iD functionality. Getting the monkeys on my ISP’s helldesk to accept that there is a problem and report it upwards is a painful, endless task of the type described in Dante’s Inferno. It could be a long time before I can use iD again.
