What I wanted to call rules are very easy ones. For example, it has to be used after a phrase or some phrases.
The key of when to use "、" is how a sentence is easy to read.
I'll show you an example in Japanese.
If you want to say, "I saw Mr. Yamada at Tokyo station yesterday evening." in Japanese, it's translate as
昨日の夜、東京駅で山田さんと会いました。(I think it's natural.)
昨日の夜、東京駅で、山田さんと、会いました。(Some people do that, but I think it's hard to read. So many "、")
昨日の夜東京駅で山田さんと会いました。(Some people do that, but I think it's hard to read, however, I prefer this one than second one.)
>> I found the following sites but they all don’t offer very specific rules for the comma.
Yes, that's right. There is not a solid strict rule. It depends on the writer. Because punctuation and comma didn't exist in Japanese before the 20 century. As Nobu wrote, you put a comma to make the sentence read easily. It's the general rule that students learn at school. He showed good examples.
Personally, I am the person who put extra commas. I don't correct commas, (Did I? sorry) but when I write an explanation in the notebook section, I might write commas unnecessarily in my Japanese sentences. Because I think putting in commas makes the sentence clearer and lets the learner understand better. If a Japanese person read it, it looks annoying, but how about the learners? Do they think it's strange and hard to read it? I don't know. I'd like to hear from learners. It's an interesting question. I'd like to hear from Japanese teachers too.
Overall I agree with Nobu. The way of using commas depend on people and it is their writing style. As Nobu says, learners don't have to take it too seriously, even if your commas are corrected. But, putting three commas in a sentence is not good except for emphasizing the meaning of the words.
Is there a good sure that explains the rules? I found the following sites but they all don’t offer very specific rules for the comma: