I think it depends more on how cynical and/or confident the person you are talking to is. A cynical person will assume you are insincere even if you aren't. An unconfident person will think you're just being polite.

It really, honestly doesn't. A good conversationalist knows how to draw trust from their partner. One of the great benefits of learning how to listen and respond with genuine interest is that you can pierce the walls people put up. There is no one 'key'; it only comes with practice.

Personally, I have never met an adult[1] in my life who can start a sentence with "Wow" and come off as convincing. "Wow" just sets off my bull shit detector (rightly or not).

Albeit that doesn't prove you are wrong. It could also mean I haven't ever met a "good conversationalist" who has used that word with me.

Seeing as I have read "How to Win Friend's An Influence People" (twice) and 90% of the people I know do the exact opposite of what the book suggests, it could indeed be I have never met those people.

It's not that there aren't things they can say that would be convincing, just the specific quote the OP used -- "Wow. That sounds hard” -- would not only be not effective on me, it would be detrimental.

[1] I have to specify adult because I have met children who use it convincingly.

When considering soft things like conversational flow, try not to get too focused on the use of any one particular word. Look to the intent behind the phrase. "Wow, that sounds hard" is fundamentally 1) an expression of genuine acknowledgement, and 2) an opening to learn more about what is clearly important to the person you're talking to.

The skill is in finding something about your partner that you can say these things honestly about. You do that, and whatever actual words you use to express it don't really matter that much. The emotional intent behind your words will ring clear.

In the original version I heard from him, perhaps on his podcast, he mentioned that he usually uses a stronger exclamation than that but hs a policy of not cursing in whatever publication the written piece appeared in.

I disagree. If you're already defensive about your job, you may be prone to misinterpret that statement as sarcasm, even when delivered perfectly.

I imagine there's safer comments or questions you could go with.

Round two is likely something like "no, I don't think I could do that, it sounds hard to me. You have skills I don't "

But it has to be genuine. You can't read a script, you have to mean it.

You're right, in that there are some people that are minefields. But I do think most people who aren't natural conversationalists greatly overestimate their number. Most folks genuinely want to connect, and it only takes the slightest of pushes to break the ice. Extrovert, introvert... It doesn't really matter, in terms of short-length discussion. People are people.