Here's page 24 of Fusion #15, and we see that bridging between multiverses requires someone on both sides to open the door. But what is this OM-Mat that'll going to come through the bridge?
So, it is actually possible for matter to travel between multiverses, just it's extremely difficult, probably only small amounts of matter can pass and it can wreak havok.
Now I'm wondering what about inmaterial beings (like bob?), either those made of energy or pure consciousness. Could they cross over multiverses safely?
I haven't talked to Whistler, so I only can only infer from the details of this story arc (and I won't get into the details for sake of spoilers). That said, I would suspect beings of energy couldn't safely travel to another multiverse (energy is still a "thing"). As for pure consciousness, I'd think it also wouldn't be safe, since, although "consciousness" as a concept is safe, a being of any sort would have to have some form to exist (material, energy, or something else), which would likely interact unexpectedly in another multiverse.
Whistler originally had a bit more exposition about the energy surges and how they'd dissipate harmlessly because they're in the Fuzz instead of in a set universe; but the discharges could do some (non-lethal) harm if they touched anyone (sort of like a static discharge). I cut the extra bit because of panel arrangement and slowing down the momentum and urgency of creating the bridge.
Whistlers don't reincarnate; the ghost of the previous Whistler helps train the next Whistler, who is a person with some sort of supernatural ability/connection (which the person may not even be aware of). The current Whistler had a foot firmly in the world of the supernatural long before Lamont (whose corpse we saw briefly on page 2 of Issue #4) showed up to let him know he'd been chosen as the next Wandering Whistler. As a strong hint at what this "foot" was like, if I ever get around to a Wandering Whistler series (which I'd love to do and have a decent bit of story sketched out), the first issue would be titled "Modern-Day Charon."
