If the writing is less formal (and I think most comments and even most documentation is somewhat informal), you can sometimes just address the reader directly, as "you".
For the most formal writing most people will ever encounter, one can use "one" as the singular pronoun of indeterminate gender. Alas, I suspect "one" confuses as many people as a singular "they"; in additional to grammatical confusion ("one *what*?"), the formality itself can be a barrier to students who are feeling overwhelmed. The passive voice also has a tendency to creep in more with use of "one."
I'm personally fine with singular they, unless the context is very formal. I personally prefer to remedy that confusion by using a less formal style. The people I've met who had genuine and lasting difficulty with singular "they" even in informal contexts were ... at a stage of life where they were unlikely to take up new hobbies as intricate as programming.