To use or not immutable?

[Jack via Digitalmars-d-learn]

I'm coding with visual studio code and now it shows a yellow mark 
on variables that is never modified and that could be marked as 
const or immutable. I think that makes sense, so I think I'll be 
using it. Do you use it in your code base? are there some design 
flaws, like there's in C++'s const, which I'm not aware of?