Increasingly + positive or increasingly + comparative?

For instance, would you rather say "It became increasingly hard" or "It became increasingly harder"?

From my understanding, both are possible, but their meaning is slightly different. The first simply means that it became "harder". The second literally refers to an increasing rate of getting harder.

Though in practice, I believe the second is still used to express the exact same as the first, while sounding somewhat awkward.

You should say:

It became increasingly hard.

This is mostly because there is an inherent (if obscured) redundancy in the second phrase. The word harder already has a sense of time and progression to it. Harder implies that it used to be less hard but is now changing toward being more hard. So saying "it became increasingly harder" doesn't really add anything new or make the sentence more clear, it just seems to make it increasingly more awkward.

"Increasingly harder" is an example of a classic grammar error in English of trying to express the same idea two different ways at the same time.

American children often say "more better", and their teachers will scold them and tell them to either say "better" or perhaps "more good".

I understand how one might suppose that "increasingly harder" should mean "getting harder at an increasing rate", but that's simply not what the words mean in English. It may be logical, but it isn't accepted English grammar.

Correct usage is to say, "It became harder", or if you want to add some emphasis, "It became increasingly hard".