I am wondering how many characters are available in a microblogpost of the Microblogging for Confluence add-on.
A character limit is currently not available and is not planned. Each user can decide how much or little they write.
As an administrator, however, you can specify how many posts and comments are displayed in a microblog timeline before a button for loading older posts and comments appears.
We plan to limit the height of any single contribution using a “Read more” button in a future version.
If you have further questions, just let us know.