British comedians and satirists are struggling with the same problem that confronted American entertainers in the months after 9/11: how to acknowledge the terrorist elephant in the room without insulting anyone or bringing the mood down. For comedians, who frequently operate on the razor edge of good taste, anyway, the July train bombings in London are a delicate matter. If those comedians happen to be of Middle Eastern descent, well, then, the pressure is even more intense. Some comics are gingerly beginning to talk about the bombings, but “for all the effort at cheerful revenge, none of the dozens of acts addressing this year’s hot issue know quite what to say about it.”