When writing dialogue, a dash can be used to denote interruption. For example:
“Hello, can I ask you about—”
“No.”
If a character is interrupting themself, should the first word of the interruption be capitalized? In other words, should the word oh be capitalized in the following quote?
“Have you seen — oh my God, you’re him!”
Best Answer
Jane Straus advocates lower-case to follow a dash even after a sentence fragment:
To adapt her comments, This shows an abrupt change in thought and warrants an em dash.
Usage on the internet is non-uniform.