Questions about example sentences with, and the definition and usage of "Oftener"

A:
For standard English “no oftener” would be considered incorrect, it should be written as: “no more often than,” or “not as often as” but either is far less common and formal than simply saying “less than.”
Examples: The trees fall no more often than their leaves.
There are fires no more often than lightning strikes.

Frankly “no more often than” will sound clunky to native speakers, I would just stick to “less than,” it’s easier to say and to understand.

A: thanks. I’ve found it in grammar book 😂 and it sounds strange, so I decided to make sure that I’m correct

A: If the -er form exists, then it is preferable. There is no difference in meaning, however.

Also, note that while "oftener" is valid, it is somewhat obsolete and it is rare to hear it these days.

A: One syllable adjectives and two syllable adjectives ending in "y" should have comparatives with "-er", all other adjectives and adverbs should use "more"

angrier is preferable to more angry
clearer is preferable to more clear

oftener is more or less obsolete, more often is preferable

A: often -and- more often