Fast radio bursts are among the strangest signals in astronomy: intensely bright, brief flashes of radio energy arriving from far beyond the Milky Way. Most appear once and vanish into statistical memory. A repeating burst changes the emotional texture of the problem because repetition implies structure, and structure suggests mechanism.
That is why periodic or semi-periodic repeaters feel so unsettling. The universe is not just shouting. It is keeping a rhythm we still do not understand.