Rework future tense in user-facing messages

[lucperkins]

Motivation

There's a tendency that a lot of us have when writing English to use a kind of "fake" future tense to express regular or expected connections between things. In general, though, it's better to reserve the future tense for things that will happen in the future and use simple present tense to express "if x then y"-style connections. Changes correspond to this PR.