Perhaps I should add that when I said 'idiot proof' and 'idiot resistant' , I was NOT calling anyone an idiot for using it -- I LIKE stuff that's idiot-resistant as it greatly reduces my own chances of making stupid mistakes.
All I meant was that some users make wildly exaggerated claims for two-bath (especially Diafine, for some reason). Yes, it is very tolerant -- but equally, yes, you can go beyond even its tolerance levels, for example by using it too cool; or leaving the film so long in the first bath that significant development takes place in that bath (many two-baths can be used as fine-grain, speed-reducing developers by omitting the second bath and greatly extending the first); or not leaving the film in the second bath long enough to exhaust the developing agent; or of course any combination of the above.
It also tends to be in the nature of two-baths that they are compensating developers, so either you like the tonality for your subjects, or you don't.
Cheers,
Roger