Why do some injuries scar, and others don't?

Ok, heres your chance to laugh at me a bit: About 10 years ago I did the idiotic thing of using a weed whacker while wearing shorts:eek::rolleyes:. (hey, at least I confess to dumb things I’ve done to everyone. Why should my wife be the only one who gets to laugh?:p) Yes, I somehow whacked the lower section of my leg. It didn’t bleed, but to this day there is a scar.

When I was about 12 I got into a nasty fight and both of us ended up smashing through a plate glass door. My left hand got cut to ribbons. I mean CUT, really, REALLY bad. I almost bled out. The cut was large and deep, and long across. 30+ stitches.
Yet I have no scar what-so-ever from this.

When I was in the first grade I got bit by a dog on the back of my left leg while I was walking home from school. It wasn’t a very deep bite, and bled very little. Very few stitches.
Almost 40 years later I still have a scar.

In the fall of 1996 I took a dive while riding a motorcycle. Cut up my foot and my arm pretty good, and deep. I have no scars to prove this.

So, why do some injuries scar, and some don’t? From my examples the extent of the injury doesn’t seem to be the deciding factor.

There’s probably a number of factors, and I’ve listed a few below. I once fell on my face while biking and scraped it up pretty badly - the doctor told me to wipe it with a warm wash cloth every few hours to get every little bit of scabbing off, since scabs lead to scarring. Well I did, and there’s not a scar or blemish in sight!

This site says the following:

This link says that certain scars like a Keloid scar “grow beyond what is needed at the site of an injury. This type of scar is caused by too much collagen forming while the skin is being repaired. The tendency to develop keloid scars is genetic.”