The sentence “Dicit se paenitere quod legato rumores referenti crediderit” is an Indirect Statement of an impersonal construction (using the verb paenitere). It has been translated (in “Learn to Read Latin”) as: “He says that he regrets the fact that he believed the legate reporting rumors”.
Why has subjunctive (“crediderit”) used and not indicative (credidit") for “he believed”? Alternatively, why “crediderit” was translated as “he believed” rather than nonfactual (“allegedly he believed”).
Thanks.
I suggest you look on page 275 of your text book.
If an indicative appears in a subordinate clause in indirect statement it is because “it’s an addition of the writer or speaker of the sentence” or because “it contains information vouched for by the writer or speaker”.
The subjunctive in a subordinate clause is “to be understood as part of the original statement or perceptions being reported indirectly”.
This is the second question you have asked about indirect speech. Ask as many questions as you like but I wonder whether the textbook you are using sets out things clearly enough for you?
Please do not be deterred from asking more questions. That’s what the board is for. 
Thanks for the clear explanation.