No me gusta el tono de ese comentario.

Because gustar works differently from to like in English.

In English, I am the subject in I like the tone.
In Spanish, the thing that is pleasing is the grammatical subject. So in:

No me gusta el tono de ese comentario

the subject is el tono de ese comentario, and me means to me.

So the structure is closer to:

• The tone of that comment is not pleasing to me

That is why Spanish uses me gusta rather than yo gusto.

Because the subject is singular: el tono.

With gustar, the verb agrees with the thing being liked, not with the person who likes it.

• Me gusta el tono = I like the tone / The tone pleases me
• Me gustan los tonos = I like the tones / The tones please me

Here, tono is singular, so the verb is gusta.

Me is an indirect object pronoun, and here it means to me.

So:

• me gusta = it is pleasing to me
• te gusta = it is pleasing to you
• le gusta = it is pleasing to him / her / you (formal)

In this sentence, me tells you who does not like the tone: I do not like it.

In Spanish, no usually goes directly before the conjugated verb to make the sentence negative.

So:

• Me gusta el tono... = I like the tone...
• No me gusta el tono... = I do not like the tone...

This is the normal and straightforward way to negate a sentence in Spanish.

Spanish often uses de to show a relationship between two nouns, where English might also use of.

So:

• el tono de ese comentario = the tone of that comment

Here, de links tono and comentario.

It tells us which tone we are talking about: not just any tone, but the tone of that comment.

These words all mean something like this/that, but they point to different degrees of distance.

• este = this, near the speaker
• ese = that, near the listener or a bit removed from the speaker
• aquel = that over there, farther away

In modern Spanish, especially in many everyday situations, ese is very commonly used for that.

So ese comentario simply means that comment.

Depending on context, este comentario could also be possible if the speaker feels the comment is very immediate or close, for example something just said or just written in front of them.

Here tono is most likely figurative.

It often refers to the attitude, manner, or way something was said, not only the physical sound of a voice.

So in this sentence, el tono de ese comentario probably means something like:

• the attitude behind that comment
• the way that comment was phrased
• the feeling or edge in that comment

It could be critical, rude, sarcastic, dismissive, etc.

Because Spanish usually uses the definite article more regularly than English does.

Here el tono means the tone. Spanish normally includes the article when talking about a specific noun like this.

So el tono de ese comentario is the natural way to say the tone of that comment.

Yes, but it means something slightly different.

• No me gusta ese comentario = I do not like that comment
• No me gusta el tono de ese comentario = I do not like the tone of that comment

The first sentence rejects the whole comment.
The second is more specific: maybe the content is not the main problem, but rather the way it was expressed.

So the original sentence can sound a bit more precise or diplomatic.

Yes, but the original order is the most neutral and natural:

No me gusta el tono de ese comentario.

Spanish can sometimes move parts of the sentence for emphasis, but that changes the focus a little.

For example:

• El tono de ese comentario no me gusta.

This is still correct, but it puts more emphasis on el tono de ese comentario.

A learner should usually stick with the original word order unless there is a special reason to emphasize something.

Not normally.

Me already tells us to me, so:

• No me gusta el tono de ese comentario is complete and natural.

You can add a mí for emphasis or contrast:

• A mí no me gusta el tono de ese comentario.

This might suggest something like:

• I do not like the tone, even if someone else does
• As for me, I do not like that tone

So a mí is optional here, not required.