I can imagine a sanity-like mechanic would be useful for handling the consequences as the PCs get progressively more disconnected in time, probably while loading up on all sorts of enhancements based on poorly-understood tech looted from fringe human factions or alien tombs.
EP has a sanity system, and going insane is one of the only ways to have your character permanently die (if all of the backups are corrupted too). Sure, therapy is very effective in the game, and psychosurgery can overcome many traumas, but the list of things that can cause mental stress is pretty big (including inflicting or even witnessing excessive violence) and your sanity can die the death of 1000 paper cuts if you don't make your character with a fairly strong willpower. You can also start out hardened against certain types of traumas, but doing so is basically mental scar tissue that gives permanent penalties to all sorts of social actions, so there is a cost to it. Keep in mind too that witnessing asynch (psionic) powers will also sap your sanity, and this category cannot be hardened against, so a group with an asynch is already hurting themselves (yes, the sanity hit includes the user of the powers too).
Again, this is why it's so important to keep regular backups. Have a fight that goes poorly where you survive, but lose a bunch of sanity? Revert to the you of 5 minutes ago and play through a lite simulation of what happened in time accelerated space! Then, afterwords, when you've got time to spare, just fork up a dozen copies of yourself, play the unedited sense-inputs, keep the ones that crit-succeed all their SAN saves, and overwrite your own traumatized self with that luckier version of you. Bam, subjective continuity of experience into the best of all possible versions of you!
When you actually are data, the Alpha Centauri Hive quote becomes horrifyingly true.
Most people (including most PCs) don't have those options at all times. You have offline backups that you update monthly or maybe weekly, not every 5 minutes. Also, systems that allow time compression are a scarce resource, either costing you big money or rep to gain access, and that assumes the owners don't object to the illegal/unethical/forbidden practice of running multiple forks. Lastly, reintegration those forks may or may not be without risk depending on how long ago the divergence happened and how significant it was. So, just because some characters in EP might be able to do what you suggest, doesn't mean it's practical to do so (nor is it even remotely common).
It is common to update your off-site backup less frequently. But stacks update multiple times a second. Copying and writing a mind-state is not something which takes significant time with Eclipse Phase basic consumer-grade electronics. I'm not sure what changed in 2E, but in 1E, you can run minds in basic PC-owned PCs just fine, and one more time, there is no risk to reintegration, because you can note "Whoops, lost some sanity there.", wipe yourself, and run the reintegration again and again until you get it right. And really, you don't particularly need to reintegrate with a divergent fork; you can just rip out their cogitation with psychosurgery, play back their memories to a fork of yourself, then stack merges of those forks until reintegration is just barely possible with a critical success, then spam attempts.
And finally, the stops on going horribly posthuman are not strong at all. Many habitats are fairly anarchist and are not set up to deal with a tragedy-of-the-commons repeated-forking intelligence copying themselves everywhere and absorbing every available-to-all computing resource. The more capitalist habitats run into the problem that a horribly optimized posthuman is a much better economic resource to allocate into your scarce supply of bodies than an economic infogee, and the habitats which try to enforce their objections with force run into the problem that it's really, really hard to kill a sentient program which can steal every robotic body they can get physical access to and plug a copy of their hot-swapped cortical stack into.
The options existing are setting fiat too, so it's fine to have the same setting the limits. If you can accept that these things are possible, then you should be able to accept that the (smarter than us) transhumans have been able to anticipate them and set measures to counter them too.
If you want to go down that road, then you should accept that the smarter-than-transhuman horrible posthuman collective intelligences should be able to counter the countermeasures, since they are not constrained by ethics and can run themselves in parallel, after psychosurgering themself to think of nothing but solving the problem, then wipe themselves and just take their plans and conclusions to implement.
But even if we posit equal intelligence between posthuman and transhuman factions, then there is a massive asymmetry in ability. Going forkswarm is like, in our world, being a smart visual-symptomless zombie virus that can also spread themself via spam emails. It doesn't matter how smart your smartest opponents are. It matters how many people you can quietly compromise before zerg-rushing those very clever transhuman opposition agents.
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Also, since people seem to be interested in this topic beyond just the game-state of Eclipse Phase, I can recommend the book Age of Em, by Robin Hanson.