Uh, like all traits, you can just lie about it.
So when they ask you what your strong suits are, you add "intellectual curiosity" to the list. Already you sound smarter!
Now if they ask you one of those "tell me about a time when", you try and mix your inquisitiveness into the mix. Maybe you didn't just help the junior developer learn about xml, but you also looked into the way your project was using xml, looked up a more efficient way to do it, and then worked with the junior to improve output by 12%.
ProTip: always know how you got that figure, even if the figure itself is, well, not fabricated, but possibly an imaginative rendering of reality?
If you want to ask questions (and you should), just ask questions along the business domain of the company. "How does this generate revenue" and "what problems can tech solve to help grow the company" and the like are good hooks. It is easier to meaningfully talk business needs than have someone draw a few circles to represent the company architecture and then work out what to ask from that. That shows you have business concerns, which all IT companies really want from the nerds.
Your first part "how much do interviewers value inquisitiveness" is unanswerable, some will a lot, some won't at all. You have to work that out on your own. Tyoically they like it, and they also like it when candidates show they did work beyond what was asked of them.