Is there a risk in scarring your followers?
I've misread the wiki:
Wound are a representation of your followers' mortality. Each failure of cult business (of the types that may cause wounding) or exploration may cause your follower to become Wounded. Wounded followers are not available to use as followers and may only be cured by Talking with them and using 1 Funds. Followers that were not cured by the time the Season of Sickness rolls around will die. Cured Wounds turn into Scars.
Three Scars of the same type will kill the follower.
A follower can have only one wound (which can kill him when he'll become sick), but up to 2 scars of the same type (3rd one will kill him/her). It is worth to point that there are only 3 wound types (giving +2 EDGE, KNOCK or WINTER), so the chance of accidentally getting 3 of the same types is quite high.
So it seems that doing it on purpose is a bit risky unless you have lots of followers to spare, however, a follower with 2 KNOCK from a scar gets so much more valuable, since 2 KNOCK enough for most of the summoning (actually, having any additional 2 points in another aspect is a huge bonus!).
So it might be worth to force a follower or two to get a scar for that extra 2 KNOCK points. Yes, there is a risk, but later on in the game you will be using mostly followers for summoning spirits and let the spirit do the hard, dangerous work.