When you top your plants from seed, use the Uncle Ben's technique to get 4 tops with 1 snip. I do it all the time and it works just fine.
Don't worry about that scar, it happens (especially on the lower, older leaves), but if it gets excessive, and new growth starts to suffer, then its something to be concerned with. Otherwise, if the plant looks and feels healthy, then keep doing what your doing.
Good Luck!! I am also growing an AK47 right now and she is in her second week of flower.. Stretch has pretty much come to an end, and she is budding up nicely.