^ The problem is that deleting a thread is permanent. FMods are volunteers so all of their powers are designed to be reversible by staff members, if necessary. You can imagine the chaos that would happen if a FMod was hacked and deleted all the threads in a forum, lol.
Jagex staff members do have that ability but use it very rarely (for example, if they wanted to completely reorganize a forum section).
Anyways, I agree that Toxicity is great. She's been around for as long as I can remember. I think she is particularly good at explaining the reasons for her decisions in locking messages.