Sounds reasonable in theory but there are some undocumented commands that have been around since the year dot. sp_msforeachdb being a case in point.

Perhaps in the old days not documenting stuff on an ROI basis had some validity but in the collaborative world who says that the documentation has to be written by central group?

At the moment there are all sorts of articles out there on how to use the undocumented commands but why not have a community contribution resource so the workload shifts from being "write documentation casting pearls before swine" to "verify documentation from the truffles that have been unearthed".

I think it is valid to have a documentation category that emphasises that the commands are for diagnostic and testing purposes and (while written by professionals) may contain nuts bugs.

The other thing I have to mention is that there is a M$ course which goes down deep into the SQL Internals and discusses how to interpret DBCC PAGE and others. I was one of five DBAs who came out of that course on day one feeling humbled and the colour of stupid worrying about the remaining 4 days on the course. To some extent these commands have been documented but the info isn't on general release.