I have to wonder if this means that all the ancient Romans kind of smelled a little poopy all the time
Well, the sponge itself would be rinsed of fecal matter in running water, and the salt water/vinegar soak would have taken care of the rest. Smell (at least, the smell of the wiped Romans) wouldn’t have been a problem - transmission of parasite eggs from fecal matter, on the other hand? Probably a non-negligible issue.
https://www.livescience.com/53303-ancient-rome-infested-with-parasites.html
It was pretty bad.
Pre-germ-theory food handling and water source management always took a toll, so I’m guessing poo sponges were a relatively small part of the problem. Especially if the vinegar soak actually worked at all.
He also reviewed studies analyzing Rome’s ectoparasites — that is, parasites found on the outside of the body, such as fleas, lice and bedbugs — in textiles and combs.
Surprisingly, ectoparasites were just as common in the Roman Empire, where people regularly bathed, as they were in Viking and medieval populations — groups of people who didn’t bathe frequently, Mitchell found.
Now that is surprising. How hard is it to just delouse your shit before you put it back on?