1. Ofc, you will start with Spellthief's Edge but it's actually pretty helpful to just by potions alongside. First of all, you never know how long the laning phase will take before the first recall and secondly the benefit of the additional Stealth Ward is pretty low. In the early laning phase there is hardly any opportunity for leaving the lane to place a ward in the river area, you will likely do this after your first back/ the purchase of Sightstone. The two Stealth Wards are absoluty sufficient if being placed alternating or at two lane-near places.

2. Supports actually have to travel the map even more because the addition of Sightstone implies more recalls with more situations you want to save gold in base and just opt for more Vision Wards. Karma can actually abuse the additional mobility by catching up followed by using her Q or W. I just simply don't see the reason for wasting 200 more gold into boots which are currently the worst ones in the game because their unique effect is rather weak. 200 gold is worth two Vision Wards.
Ofc, CDR boots are just an option in case of not risking to build more CDR than actually required but my point was rather to emphasize that even all of the other boot options offer more benefits.

3. Well, the idea behind building penetration and CDR based AP items (you missed out this part of my statement here) is the gold efficiency and overall lower gold investment. If taking a look at an item such as Zhonya's Hourglass one of the two build path components is way too expensive without providing any furthermore useful stats. The point of building CDR/ Mana Regen (AP) items is clear I believe. I would just swap ZH for a different item then!

4. Graves basically has more resistances than other AD Carries making him less vulnerable to Karma's early game damage, that's the actual encounter. Overall her damage seems lackluster after a short period of time in lane. If you compare Karma's damage to Vel'Koz' damage it's pretty low but ofc, she provides more utility to the game. If you compare Karma to Janna then the amount of utility provided by Janna is far better, her shield is stronger etc.. It's just that you have to consider these things to explain why she doesn't see that much games anymore compared to before at some stage.

A few suggestions:

• There is also the possibility of just buying potions alongside Spellthief's Edge on spawn. It provides you more sustain and nearly the same amount of vision control.
• Mobility Boots > Boots of Swiftness; they are less expensive and allow you to rather spend money on more important items; the roaming ability is even more insane; otherwise you can even opt for Ionian Boots of Lucidity or Sorcerer's Shoes; problem with Swiftness boots is simply that they have nearly the same effect as Mobility boots but the additional passive stats are too weak imo to be worth spending the extra gold on
• Penetration/ CDR items > flat AP items (concering damage options)
• one of her current weaknesses are the popular ADC picks ( Graves and Sivir) and it seems like her damage in lane is just overall underwhelming
• I'm unsure about recommending a full offensive rune setup, people might fall for it without considering the alternatives :o

Thanks for the credit. when seeing the guide in the first place I couldn't remember you :o