For writing fiction, I don't use semicolons in dialogue (spoken or thoughts) and I don't use it in prose.

That said, I am in Galastel's camp on other forms of punctuation indicating to the reader various lengths of pauses in a character's speech, or verbalized thoughts. sometimes to take a breath, or to think -- or cut short a sentence and change their mind about what they are saying. Perhaps to hesitate before saying something crucial.

I believe in practice that this is how people actually read, that they will read those pauses and hesitations into the dialogue. The reason I don't use semicolons is I think most people are not sure what to do with them. Also, in Galastel's table, if I want a medium pause, I'll use a dash or em-dash. The semicolon is redundant.

To me there is a difference in pacing for the following sentences:

(1) "Do you want red blue or yellow?"
(2) "Do you want red, blue or yellow?"
(3) "Do you want red, blue, or yellow?"
(4) "Do you want red, blue -- or yellow?"
(5) "Do you want red, blue ... or yellow?

(1) is spoken in a rush.
(2) is normal, but (3) is spoken more deliberately slowly around the color choices to give each fair consideration, as if the person speaking is showing samples of the color, or pointing at them.
(4) has a more dramatic pause after "blue" that will emphasize "yellow", enough for the listener to notice but not to think about interrupting.
(5) the ellipsis causes a long enough pause that the listener will have a thought in-between, it seems like the speaker is mentally occupied after the word "blue", thinking or searching for something, or is more deliberately pausing for dramatic effect.

I think in practice readers "hear" dialogue and verbalized thought as spoken speech and as authors if anything is said in an unusual or unexpected matter we should indicate that with punctuation, including (very rarely) emphasis by italics. I don't think the same rules apply in prose as are applied to dialogue or verbalized thought (in italics, without quotes, but like dialogue in separate paragraphs and tagged as thoughts in non-italics).

Verbalized thought example:

That lady is bad ass, Cheryl thought.

For writing fiction, I don't use semicolons in dialogue (spoken or thoughts) and I don't use it in prose.

That said, I am in Galastel's camp on other forms of punctuation indicating to the reader various lengths of pauses in a character's speech, or verbalized thoughts. sometimes to take a breath, or to think -- or cut short a sentence and change their mind about what they are saying. Perhaps to hesitate before saying something crucial.

I believe in practice that this is how people actually read, that they will read those pauses and hesitations into the dialogue. The reason I don't use semicolons is I think most people are not sure what to do with them. Also, in Galastel's table, if I want a medium pause, I'll use a dash or em-dash. The semicolon is redundant.

To me there is a difference in pacing for the following sentences:

(1) "Do you want red blue or yellow?"
(2) "Do you want red, blue or yellow?"
(3) "Do you want red, blue, or yellow?"
(4) "Do you want red, blue -- or yellow?"
(5) "Do you want red, blue ... or yellow?

(1) is spoken in a rush.
(2) is normal, but (3) is spoken more deliberately slowly around the color choices to give each fair consideration, as if the person speaking is showing samples of the color, or pointing at them.
(4) has a more dramatic pause after "blue" that will emphasize "yellow", enough for the listener to notice but not to think about interrupting.
(5) the ellipsis causes a long enough pause that the listener will have a thought in-between, it seems like the speaker is mentally occupied after the word "blue", thinking or searching for something, or is more deliberately pausing for dramatic effect.

I think in practice readers "hear" dialogue and verbalized thought as spoken speech and as authors if anything is said in an unusual or unexpected matter we should indicate that with punctuation, including (very rarely) emphasis by italics. I don't think the same rules apply in prose as are applied to dialogue or verbalized thought (in italics, without quotes, but like dialogue in separate paragraphs and tagged as thoughts in non-italics).

Verbalized thought example:

That lady is bad-ass, Cheryl thought.