They say LST is completely safe for Autos. Many Auto growers get all the results they really need from that in terms of yield. Topping has always been a controversial subject with Autos. Though, this article seems to indicate yes it's OK if the plant is healthy:
by Nebula Haze Yes, you can top an auto-flowering plant that is growing fast and healthy. For example if it has grown at least 4-5 nodes (pairs of "real" leaves) by the end of week 2. Otherwise it may not be growing fast enough to handle topping without getting stunted. Read on to learn more!
www.growweedeasy.com
I would personally approach defoliation on a leaf-by-leaf basis. I don't think I would do a broad sweep with an Auto like I did with Wilma Wonka.
On a side note, you might be on to something with that "red stem" thing. I reviewed an older photo of my plant and don't see the red stems as much. Now I am starting to question whether or not the pen tester I have been using for pH testing is calibrated right. Then again, I suppose red stems could be a genetic trait that comes out with maturity for this strain, too.
30 days from soil breach (pictured)
80 days from soil breach currently
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Please ignore my poorly executed first attempt at cloning on the right