Earlier quoted context omitted.
Much of the point of a dog whistle (as I understand it) is plausible deniability. The parent comment stands: shutting it down over something that "may mean something" -- even though with context you may be quite sure -- is a bad look. The next step is simply to point at the myriad of other times anyone called someone a rat on Twitter and Twitter is left to defend a position of shutting people down over what they were…
Or we should just be willing to call dog whistles what they are and stop feeling the need to respond when people cry 'but that person used the word rat over there!'.
It's pretty clear that the difference is context, but I also don't think there can be clear guidelines if Twitter is expected to delve into the context for each tweet its users make.
In fairness, context typically doesn't provide smoking guns as pungent as this one. I'd still say it's not beyond reasonable doubt (and I'd guess most would be ok with that for a Twitter ban -- it's not prison or death).
So, sure, everyone should call it a dog whistle on the preponderance of evidence, but there were almost certainly better grounds for the ban. I doubt there will ever be a good ban target whose only giveaway is dog whistles.