Is there a character limit on ticket comments?

Question

How many characters can be added to a single comment?

Answer 

Yes. The character limit on ticket comments using the standard agent interface is 65,535. For example, if you submit a plain text comment with 100,000 characters, it will always be truncated to the first 65,535.

In accounts with Agent Workspace enabled, comments are saved in HTML format. All HTML tags and characters are included in the 65,535 limit. Truncating is not supported in Agent Workspace. This can produce unpredictable instances when the comment submission fails due to the character size limit being exceeded. 

If markdown or rich text formatting is enabled and in use, comments may be truncated even more. Extra characters are needed to encode any kind of formatting used in markdown and rich text formatting. Even if these characters are hidden, they still are counted towards the character limit.