I was reading this particular answer, when I found something interesting and confusing to me. The answer stated:
If one had to insert a particle in [会社{かいしゃ}など230の会社] that made sense, that particle would be 「の」. It would, however, be slightly wordy because there will be another 「の」 coming soon in 「230の会社」. It would also make the sentence sound unnecessarily informal as well.
It makes sense to me that it is more wordy. However, I would have guessed the opposite for formality. I assumed that by adding the extra particle it would become more formal.
So, this claim that adding the particle is 'unnecessarily informal' is at odds with my understanding.
How is it unnecessarily informal?