If you need to include a + in a query parameter, you may need to use %2B instead, due to a W3 recommendation that causes a + to be interpreted as a space.
I found it be refreshingly pedantic and accurate to refer to it as just a "recommendation" rather than a "requirement" or something... though I'm not actually sure why we call such standard things in the web APIs merely a "recommendation". Can't we just call it a standard at this point?