Renamed.

Upvoted, not for your downvote, but for raising the point that these expressions can serve as conversational signals of what LWers call tapping out. (Tangent: "tapping out" in the LW sense is a terrible appropriation of a term from a different context, because in the original context it explicitly and literally signals submission.)

Indeed. Most of the examples have a very clear conversational meaning: "that's nice, I'm not interested, but I'm trying not to be rude about it." Failure on the listener's part to understand this is not a failure of rationality on the speaker's part. I note the examples being raised are mostly clearly of this sort, rather than in a conversation that is anything to do with careful application of thought.

In other words, sometimes stopsigns are useful.

True, but it's probably worth it most of the time to avoid unnecessary conflict.

I'm torn on "it's complicated." Clearly, you're correct that it can function as a powerful semantic stopsign. But increasingly, I also find that it's actually an entirely appropriate and even useful response (or at least an initial response) to many questions, especially political/policy/legal/normative questions.

For example, imagine a poll asking American citizens the following question: "In one sentence, what would you say is the major problem with the American health care system?" Now imagine the people who respond with something like "It's complicated," and ask yourself whether these individuals might ultimately have something interesting and productive to say about health care (compared to the average responder).

Instead of saying "It doesn't predict anything" and then proceeding to ignore it, a more productive attitude would be to ask questions like: "So can we think of some kind of consequences that different foundational pictures point to?"

Reworded: instead of saying "it doesn't predict anything", [we should] ask "does it predict anything?"

In other words: don't say a theory doesn't predict anything unless you have an actual argument that shows that it doesn't predict anything.

One of Feynman's stories is about trying to get a NASA manager to quantify the risk that the liquid-fueled shuttle rocket would explode during a launch. After initially claiming zero, he finally allowed it might be "epsilon." "Now we are getting somewhere" Feynman happily exclaimed. "What is epsilon equal to?"

Some of Feynman's best stories are about running through semantic stop signs.

I don't see how this is worse than any other probability estimate when a simple calculation with good numbers isn't available. Do you consider "probably", "unlikely", or "almost certainly" to be semantic stopsigns as well? Would it be better to say "very unlikely" or "with extremely low probability"?

I'd say that's just good practice, as demonstrated by a recent thread by Phil Goetz, and generally advocated by ET Jaynes. Low probability events can be resurrected into consideration by evidence, while zero probability events can't.

To expand on Kalium's comment. Sometimes it takes massive amounts of cognitive effort to estimate a small probability, and it just isn't worth it for the purposes of some discussion. For example, it is extremely unlikely that the Illuminati have been secretly running the world governments for the last 300 years. It is extremely unlikely that ZPP is not contained in P^R where R is an oracle for the finite ring isomorphism problem. It is extremely unlikely that RIPD is going to win any Oscars. I don't need to work out exact probabilities for any of these to recognize that they are very small, other than to note that the first one is probably less likely than the second, which is probably less likely than the third.

In that context, saying epsilon to mean a small but hard to precisely estimate probability is reasonable.

Would you be equally peeved by “negligible probability”?

That is a good place to shift gears at least, if not stop altogether.

That's odd. I've generally seen 'problematic' followed by an elaborate discussion of exactly how and why, often in excruciating detail.

PG gives roughly the same interpretation of "inappropriate".

"Inappropriate" is the null criticism. It's merely the adjective form of "I don't like it."

(Though I think it sometimes means "other people don't like it".)

It is rarely useful to say that something is obvious.

I feel like the first one is at least partially unfair. It seems more like a noisy signal, since there are many appropriate uses of the phrase, such as: "It is obvious that the trajectory of this projectile as it passes through the atmosphere of Earth can be calculated with sufficient precision to predict its landing zone and evacuate persons in the area, therefore we will not elaborate on this. We will instead concentrate our efforts on methods of early detection and measurement of such dangerous objects."

The alleged "obvious" statement draws from established and relatively confirmed experience, and may be assumed to be a fact that every physicist / astrophysicist / relevant expert already knows.

We used to deliberately switch "it is trivially obvious to the most casual observer that ..." to "it is casually obvious to the most trivial observer" in order to remind ourselves that "obvious" doesn't always mean what it means.

I once saw a heated argument between two bell labs scientists where A was shouting at B "you are wrong, you are just wrong" and after 1/2 hour of loud discussion in A's office the door opened again at which point I heard A now shouting at B "your point is just trivially obvious." I thought that was pretty good, moving a PhD Princeton Astronomer from "wrong" to "trivially obvious" in less than one hour. Agile minds!

I don't get why this is here.

Oh, this is pretty interesting. It's a very personal warm way to end a discussion. In this case it actually seems like a good thing.