Well it is and isn't.
But I keep imagining the idea of suffixes or prefixes which cue context for sentences.
What's scary is how many of these can already be signified by the use of quotation marks.
In other words, underscoring many of these things with scare quotes allows one to hear the tocsin which alerts one to possible rhetorical abuse of the truth.
Like this is just a partial list of what I think could be signified. Use your imagination and imagine many more.
A prefix or a suffix meaning...
1. This statement is believed true but unprovable by or within conventional logic.
2. This statement is of course a paradox, and I want you to realize I know that even as I am speaking/writing it.
3. This statement is factually misleading, but deliberately so.
4. This statement is completely earnest despite your understandable response of extreme skepticism.
5. This statement is a result of human horniness. Please weight it accordingly.
6. This statement is hothead bait.
7. This statement was generated by a desire for attention and nothing more. Please see me for a "real sentence."
8. This statement says absolutely nothing. You may read it or skip it.
9. This statement has an unreliable source and every one knows he or she lies.
10. This statement is only being spoken so that you will deduce what it is really trying to say. It hasn't the bravery or accountability to state that hidden sentence.