Hola Austin

We sometimes use the imperfect indicative this way with the same function as an imperfect subjunctive in a si clause, with a hypothetical meaning, so, here in "Si hacía eso, sus compañeros lo mirarían  mal", the meaning is the same as if we said:

Si hiciera/hiciese eso, sus compañeros lo mirarían mal. 

In my opinion, when we use the imperfect indicative instead, we somehow see that as something more probable to happen. 

We even use the imperfect indicative in the second clause, for example:

Si tuviera más tiempo libre, me dedicaba a viajar por el mundo.

This use of the imperfect, instead of the conditional (me dedicaría a...) is also quite common and a bit more colloquial. 

We have a lesson about the use of si with past tenses in the indicative. The examples you see in this lesson using the imperfect indicative are expressing habitual actions, which is another use of this tense. 

I'm make a note to see if we can include this case in the dictation in a lesson. 

Saludos cordiales

Inma