when speaking of Topic (Normal) and Topic (Contrast) you used the sentence

“watashi WA chikoku shita”

for both examples. Shouldn’t one of them be

“watashi GA chikoku shita”?

I was thinking of both examples, like =好き　and want=欲しい and I got the two confused, sorry about that! The point is that Japanese has a ton of things like this that are really different from how English works.

I’ve heard people say that in English, you can set the topic by saying: “As for X…” or similar constructions.

For example, in English, I might say: “So, about the election…” and I’ve now set the topic, and someone else might then say: “Yeah, things are really bad. I’m really depressed.” and this is now going to be understood to be about the election. This is so different from if someone had said this in response to asking: “How is your mother doing?” (this sets the topic to the other person’s mother)

Realizing that we do have topic in English, but that it’s just less “prominent” in the grammar, helped me to understand the meaning of topic in Japanese more.

I think this also helped me to realize how the が marker worked. Just like topic is more irregularly used in English, and often implied by context, I think the “subject” with the が marker is often implied by context in Japanese. Understanding this helped me to get the sense of like, when I needed to specify a subject and when I didn’t.

One more thing, I think people often get confused by how “ga” is called subject because the way Japanese works is very different from English in that verbs don’t always correspond to verbs, adjectives don’t always correspond to adjectives. So for example instead of saying “I like (X).” in Japanese, you’d say “(X)が欲しい” which more literally translates “X is likeable (to me)”.

A lot of the explanations that say “well, が doesn’t always mark the subject” are ignoring the way that verbs in English don’t always correspond to verbs in Japanese…and that there is usually a way to rework the sentence in a more literalistic way where the thing before が actually does make sense as a subject.

Does this make sense? I don’t know if you’re interested in updating this guide any more, it is already very good, but if you do make any more edits hopefully you can find something in my comment that is useful!