Well, if you're trying to delete a block of code but you don't want to lose it, and you're using Git (or a similar version control system) I would commit that code to Git and then delete it.
The exclusivity of the stop index actually has a nice side effect: if you slice up to index 3 and then start slicing again from 3 onward, those two slices won't overlap.
But I wouldn't use them as an equivalent to "multi-line comments" in another language (unless everyone else on your team reading your code is already bought in on that odd use).
Pro tip: While time-boxing and removing distractions are great for solving programming exercises, they're also great for entering a flow state for the purpose of studying at school or getting difficult tasks done at work.
I'd love to collaborate with (or shamelessly copy/mimic!) smart folks like the Pyodide devs, the PyScript devs, or @notsolonecoder... but this new REPL is so new that I doubt many WebAssembly-oriented folks have tried playing with this yet!
This thought path did inspired me to rewatch @phildini and Asheesh's talk on Python & TTYs.
It's even more interesting than I remember, possibly because I care more about TTYs now than when I fist watched it!
The next time you find an if-else in your code where both the "if" and the "else" return from the function that you're in, you could think of that "else" as unnecessary.