I would still call it a bug, not a KiXtart bug, but anyway a bug.
Well, there might be a good explanation of things caused by approximation of things. I will read the article you linked Richard, and I will do this with great interest
But it still seems to be laziness to leave bugs, that may be unavoidable for complex math, as they are when it comes to simple additions. I mean, 5.9 + 0.1 is at any time 6.0 and not 5.99999999.
Another strange fact is that there is no problem doing this increment with 0.2 or any higher number. Oh well, not quite true: As soon as the last digit of the floating point number is a 1 there will be sooner or later a rounding bug that "heals" itself shortly thereafter
I see that there might be no easy fixing from Ruuds side (or any fixing at all), but still it smells fishy like the sloppy coding started in the sixties of last century that gave IT the great boost before the new millennium