Feature X isn't a competitive advantage if it's easily copied. Competitive advantages are things that others cannot attain or cannot attain without great difficulty.
If the feature is the product, then the only way someone else can copy your feature is by redesigning their entire product. That's a huge barrier of (re)entry for existing competitors, and hence a competitive advantage.
If you're worried about newcomers, there isn't much you can do to argue for competitive advantage anyway. Most software ideas can easily be copied no matter what.
Except perhaps when the idea targets highly specialized markets and your team already has experts in the topic, and only a few such experts exist in the world. E.g. high-frequency trading platforms, etc.
But in most software startups, that's hardly the case.
And my point is this isn't the definition of competitive advantage.
> Most software ideas can easily be copied no matter what.
Which is why most software doesn't have any inherent competitive advantage :)
Which is why there is now a gold mine for competitive advantage which is NOT from 'computer science' but IS for projects in 'information technology' implemented in software.