Long and short is that its uses are similar, if not identical, to English, though the rules surrounding its usage are less grammatically strict. This looked fun to translate, though, and doable, so I made an attempt below. Had to use dictionaries to pick up a few unknown kanji. Maybe someone else can smooth over the patches that were rougher for me!
"Though commas may be written various places semantically, there aren’t exact rules for their usage. When it comes to conversations, we usually use commas to indicate short pauses.
Commas tend to be placed after roughly every ten to twenty characters, though there are many reasons why they may be used after fewer.
-Immediately following a subject (Ex.: 私は、あしたがっこうに行きます。) (This is such a Japanese-specific case, I don’t see a way to translate it while preserving the comma usage; here it is minus some kanji.)
-In situations where you’re listing several words (Ex. I went to Tokyo, Osaka, and Fukuoka.)
-After a conjunction or interjection (Ex. Therefore, after all, oh, etc.)
-After a conjunctive particle/phrase (Ex. He said that, and followed me.) (Not sure on this one!)
-After phrases that signify times or conditions (Ex. After an hour, the thing I’d been worried about happened.)
-To break up meanings/ideas (Ex. She was smart and cheerful, a person with a beautiful smile.) (Also not sure the way I’ve phrased this really helps present the rule. This is another case where I don’t think there’s a way to carry the comma usage over into English that wouldn’t be at least somewhat awkward.)"
That’s how I’ve seen it approximated in English before, especially with short statements of intent/ordering (Ex.「私は、ビールだ。」(“I’ll have a beer/as for me, beer,”)), but that phrasing is so much less natural/common in English, I’m not sure if it’s a great way to convey the meaning or use of punctuation.
Yeah it’s cause we basically don’t have a better way to differentiate the topic of the sentence in a way that looks similar to the layout of Japanese text.
Cause really, it’s “I (as the topic of this discussion), tomorrow to school going.”
Oh, and my biggest take away from the responses to my question and the more I read about it was that it’s really up to the individual. You can use a comma or not, but it’s more so simply to make it easier to read. That’s the main purpose.
However, in English, there are strict—and not so strict (I’m looking at you, oxford comma)—rules for comma usage, though not everyone follows them; so I wonder if that’s how it works in Japanese as well.
The symbol “、” is called 読点 (とうてん). It is used to denote a semantic separation or a pause. Compared to comma in English, the usage of 読点 in Japanese is less governed by the grammatical rules. In other words, in Japanese, the author is free to use or not to use 読点 in any place where a separation makes sense.
When two nouns are placed side by side without any particle, a 読点 is almost necessary.
Notice that he wrote almost necessary and not necessary… My feeling/impression is that reading material that is intended to learners of Japanese (Genki, Tobira, Bunpro) tends to have more commas than native material since they are trying to help the student to parse the sentences.
I know this article is old but there have been questions regarding comma usage recently in the Community forum.