geekishmatt
Any web robots should parse your /robots.txt before accessing any site, but it's still the robot's (or its programmer's) choice to use it.
So: No, but still add it to your site and maintain it.
Sometimes a subtraction of a unit is hidden-black-magic and you are switching between two models or contexts but still being in a meta-model or meta-context. (Debits and credits)
It just depends on your model or context how you interprete your value/unit relation, but this is a typical problem in applied physic, engineering or computer science :)
For a mathematican 42 or -42 makes sense - there are no units necessary. The mathematical intepretation of a negative number is just being element of a set.
For a physicist 42 or -42 are pointless, because a unit is missing. The physical intepretation of a negative number is the quantified absence of a unit.
- by the way: https://xkcd.com/435/
What is your definition of "HN material".
Try to learn few more languages an/or paradigms...