Aaron Bertrand looks at whether comments affect query performance:
Every once in a while, a conversation crops up where people are convinced that comments either do or don’t have an impact on performance.
In general, I will say that, no, comments do not impact performance, but there is always room for an “it depends” disclaimer.
I’m glad that there’s no appreciable difference. Even if there were, good comments are valuable enough to make me not care about performance implications. But fortunately, that’s not a trade-off I have to make.