TIL That the maximum length for a Steemit post title is blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah 255 characters

Yup, 255 characters.

As empirically verified while creating a new Steemit post (i.e. this one), and also via the following JavaScript code snippet from the steemit.com GitHub project:

    const maxKb = isStory ? 100 : 16
    const validate = values => ({
        title: isStory && (
            !values.title || values.title.trim() === '' ? 'Required' :
            values.title.length > 255 ? 'Shorten title' :
            null
        ),
        category: isStory && validateCategory(values.category, !isEdit),
        body: !values.body ? 'Required' :
              values.body.length > maxKb * 1024 ? 'Exceeds maximum length ('+maxKb+'KB)' : null,
    })

It also appears from the above code snippet that the maximum story body is 102400 characters (i.e. 100 Kilobytes).