It seems that 地 modifies nouns here.
This is not accurate. 地 modifies adverbial usage. The particle of speech of the word does not matter.
Is this usage of 地 common in Chinese?
The usage of 地 after adverbial is very common and standard. Use of imitative nouns as adverbial is also common, e.g. 咯咯地笑，嘤嘤地哭，叽里咕噜地说。You can think them as "xxx-soundingly" in English, e.g. "he laughed 'gege'-soundingly" = "he laughed with 'gege' sound".
At what situation is it used as such?
It's common to use imitative nouns as adverbial to describe a person or an animal making sound or movements.
And should you always need ", " to modify nouns in these cases?
Idiomatic wise, comma is the only way to connect multiple imitative words here. Conjunctives like 和 or 或 would break the 'flow'.
Think of in English, if an alien only makes three sounds, 'wug', 'tor' and 'kee', when you put them into an adjective or adverbial phrase, you don't want to connect them with 'and' or 'or'. You'll say "that 'wug, tor, kee' alien" instead of "that 'wug-or-tor-or-kee' alien". This is the same.