Thoughts
It would be very easy for SMASH to slip into not offering features because they're "too difficult."
This is one of the things that's weird about software. For any piece of software, there's a whole class of features that are possible but are often omitted because they're not 100% necessary. And people will say they're "too difficult" but nothing in software is that much more difficult than anything else. What they mean is that these features aren't 100% necessary and aren't trivial, or aren't possible to implement 100% perfectly.
And one of the reasons I'm excited about SMASH is because there are a lot of features I can imagine for a terminal that fall into this category today (using the mouse to move the cursor in the prompt or deleting selected text in the prompt or detecting whether to use control+c to copy or kill the program on Linux or automatically quoting paths with spaces or breaking the output for wrapping on spaces or updating aliases/the prompt without closing and restarting the shell or using command for keyboard shortcuts).
But at the same time there are features that are completely possible to implement, like command+f, that I'm very hesitant to implement in SMASH because it doesn't fit with SMASH's UI paradigms, in same way that selecting and deleting text isn't in the paradigm of terminal emulators.
But I think you have to make a distinction between "doesn't naturally fit into the existing UX paradigm" and "would compromise the UX paradigm." And so I think allowing command+f is the right call, even though it breaks the prompt-focused guarantee. (Where, for example, links being clickable in the output would compromise the text-only output paradigm.)