There is mention here of what I will refer to as "modulating" the flaps during the approach, rather than applying the flaps in increasing increments, at appropriate phases in the approach.
Personally, were I to see flaps being retracted during the approach, I would hope it was because climb power had been applied for the purpose of aborting the landing. Other than that, I would likely make a negative comment.
It has been said that flaps are a flight control. I disagree. They are a supplementary lift/drag control. Lift is primarily controlled by pitch. The primary pitch control provided in the aircraft is more than capable of controlling the whole range of pitch and lift required for the aircraft. The lift (and drag) may then be supplemented with flaps. However, as you are applying flaps to change the lift characteristics (we presume in the lower speed range), there is no need to further "control" that lift with flaps - the pitch control still works.
This is primarily because the drag change when controlling the plane in pitch with the pitch control is small, and proportionate. The drag change with the use of flaps can be much larger, and is very likely not at all proportionate. If your approach with a bit of flaps extended requires a brief increase in drag, sideslip (type permitted), or play with power and pitch for a moment. Increasing flap extension as a temporary means of glidepath control is poor form. If you need to do that, your approach has already been botched.
The glide ratio for the aircraft is established flaps up (unless otherwise stated). Thus, untill you have the field "made" you're not going to be extending (or extending more) flaps, until you're completely sure you need them. Once you're sure you need them, why would you un-need them!
Increasing flaps is a configuration change in preparation for a later stage of the approach, or landing. It is not to be done and undone during one approach. You would not put the wheels up and down for drag control, so why mess with the flaps? If you have spoilers, that is what they are there for. If your plane does not have spoilers, it has demonstrated ample capacity for a range of approach types, without configuration changes.
I challenge anyone to present a flight manual, or training manual which suggests modulating flaps during approach. If I were checking out a pilot who did this, there would be no further checkout, until this habit was evidently broken.
As for retracting flaps after the wheels are firmly on the ground, yes, it is advisable with caution, under certain circumstances. Retracting flaps as a means of getting the wheels on the ground is, in my opinion, only acceptable in either of two circumstances: You own the aircraft being flown, or the person who does, has directed that this technique be employed (I would be floored to hear of that!). Other than that, there is not a flight manual anywhere which suggests retracting flaps prior to touchdown is acceptable. I think that doing this is simply foolish. For all the chatter I have seen in other threads about the horrors of momentary zero G flight, this is much much less acceptable flying technique.
I have no need to demonstrate this for certification, and I would expect that were I to be caught doing it, I would be disallowed the use of that aircraft again.... I have never done it.
I propose that developing new flight techniques be left to the test pilots, and I doubt you'll see them doing it without a really good reason. If fooling with the flaps was necessary to land the aircraft, it would not get certified.