Great thread idea.
Frequentist Pitfalls:
Bayesianism vs Frequentism is one thing, but there are a lot of frequentist-inspired misinterpretations of the language of hypothesis testing that all statistically competent people agree are wrong. For example, note that: p-values are not posteriors (interpreting them this way usually overstates the evidence against the null, see also Lindley's paradox), p-values are not likelihoods, confidence doesn't mean confidence, likelihood doesn't mean likelihood, statistical significance is a property of test results not hypotheses, statistical significance is not effect size, statistical significance is not effect importance, p-values aren't error probabilities, the 5% threshold isn't magical.
In a full post I'd flesh all of these out, but I'm considering not doing so because it's kind of basic and it turns out Wikipedia already discusses most of this surprisingly well.
More generally, semantics of the posteriors, and of probability in general, comes from the semantics of the rest of the model, of prior/state space/variables/etc. It's incorrect to attribute any kind of inherent semantics to a model, which as you note happens quite often, when frequentist semantics suddenly "emerges" in probabilistic models. It is a kind of mind projection fallacy, where the role of the territory is played by math of the mind.
I've often had half-finished LW post ideas and crossed them off for a number of reasons, mostly they were too rough or undeveloped and I didn't feel expert enough. Other people might worry their post would be judged harshly, or feel overwhelmed, or worried about topicality, or they just want some community input before adding it.
So: this is a special sort of open thread. Please post your unfinished ideas and sketches for LW posts here as comments, if you would like constructive critique, assistance and checking from people with more expertise, etc. Just pile them in without worrying too much. Ideas can be as short as a single sentence or as long as a finished post. Both subject and presentation are on topic in replies. Bad ideas should be mined for whatever good can be found in them. Good ideas should be poked with challenges to make them stronger. No being nasty!