In Chandra Wickramasinghe's 2009 book, he mainly proposes comets as agents of transportation of panspermia cells. The prospect of billions of comets having had water for up to a million years, and larger, comet like objects even having permanent water, does lead him to believe they are also agents of the generation of the chiral precursors to life. He uses a lot of the most recent cometary findings to back up his case.
He doesn't go to the extent I have of thinking how far chemical evolution has gone in comets, whether an RNA world or DNA world could exist in a comet, and think why would it stop evolving? If it hadn't stopped, it may have got to a point where the proto-life in the comet may act in a way that may increase the chance of the "survival" of the comet, in the kind of attrition where comets are gradually getting absorbed into planets with hostile environments. Could actions by the proto life make it more likely for the comet to split up into two, where one of the fragments would be more likely to survive than if it hadn't split? Could chemical or biological action by the protolife make the outside of the comet black? Would that give the comets an alternative energy source for the middle of the comet to stay liquid (the original source being decay of Al 26 or otheer elements)? Could the emmission of particles from the gaps in the black exterior serve as ways to control the spin of the comet, or even course corrections (to avoid planets, or to get close enough for a gravity assist)? Could the emmission of particles get rid of unhelpful chemicals in a kind of metabolism?
In other words, if we can see evolution working in the environment on Earth that leads to eventual intelligent behaviour due to the needs of survival, why wouldn't this be the case for comets?
Principally, is there any evidence that the two most obvious features of life are plausibly existing for comets? That is, do they reproduce? Do they metabolise? Certainly, there is plenty of evidence that they "break up". How could we tell whether this is similar to a living cell breaking up, or a non-living rock breaking up? For metabolism, how could we tell whether the outgassing is making the outside more random and making the inside of the comet more ordered? Is it plausible that it is just outgassing a random selection of compounds that make up its interior? Could it be that it is metabolism regardless of whether the comet is a living thing?
The very high resolution images of Hale Bopp combined with ground observations of the spin and emission profile, may give us some ideas on splitting comets. The rate of rotation is not constant, and the axis of rotation is such that the two ends of the peanut shape may pull apart if it spins up to a fast enough speed. The change in rotation has been determined to be from the activity of the jets streaming out more in one direction than the other. From ground observations, the spin-up is more efficient than the spin-down. The conclusion is that the comet will eventually break up due to the centrifugal forces therein. It doesn't take much imagination to feel that it could be a rudimentary reproduction similar to amoebas.