Will the moderators of the Islamic section in the forum be sinful if they accept the administration's decision not to close topics containing fatwas that violate Sharia (such as prohibiting circumcision, or permitting plucking eyebrows, or considering niqab a custom) and only respond to them like any ordinary member, despite their fear of affirming falsehood and misleading sisters?

It is not permissible to keep aberrant issues that contradict Sharia (definition) evidence or the consensus of scholars in forums. Merely responding to them is not enough; they must be closed. As for issues that do not go beyond permissible disagreement, they can be discussed.

Regarding abandoning forum moderation, its ruling varies depending on the forum's condition and the moderators' ability to clarify the truth and prevent corruption. If the female moderators are capable of clarifying the truth, and there is a fear that they might be replaced by those who would cause corruption, and the section is large, then it is preferable to continue the work to achieve benefits and prevent greater harms.