If I was 17, did something cool and everyone acted shocked because of my age, I would feel like that was limit. But if my work was celebrated for its merit, then I would keep at it, doing even more cool stuff.
Let me ask you honestly though, what is the difference between a 17 year old and a 50 year old doing the same thing if both started learning to code around the same time?
The only message you are sending is that you had lower expectations because of their age. If you celebrate their work on its own, then they know they are accomplished no matter who they are stacked against. I don't care if it was a senior SWE at google who did this, I'd be equally as impressed, and that is what I want this person to know. They are not accomplished for their small age, they are accomplished period.
In general I don't think everyone's accomplishments are equal. For example becoming a medical doctor at that age is very impressive agr considered. But for the software industry, the accesibility of information and tooling makes everyone with the same amount of free time, whether a 60 year old in africa or a 12 year old in california on equal footing.
Flattery can often be harmful, especially when lacking objectivity.
