What does a question mark inside parentheses (?) mean?
(?) is simply a passing note of incertitude at the preceding word (sometimes phrase).
I am the tallest(?) in our class
Here this usage indicates that the author is not sure if he/she is really the tallest one.
I haven't seen the use of "(?)" in any book or news article for example, I would say it's something used in an informal context. But yes, I'd say it showcases the author's insecurity with respect to the statement