Q: Why Frostmourne lvl 1 early?
A: Optional. 5% slow and 10% +MS boost may net you kills easier in lane. If you can pull creeps then Frostmourne helps you clear creeps faster/easier so you can get back in lane asap to minimize danger.
Q: Why level Shield over Death Coil at level 1?
A: Shield offers 110 hp while Coil offers 100 hp. If enemies are doing first blood attempts, then instant debuff will help a lot. On top, the shield deals damage AoE while Coil is single single. This may be insignificant, but it can save lives.
Q: Why not max out Frostmourne before level 14?
A: Optional. Frostmourne only useful if you hit a target. If you are just staying back can only heal and shield, then it is practically useless. Since all levels of Frostmourne gives 10% +MS, at the very least have level 1 Frostmourne before level 10. If you find yourself able to hit enemies down, then maxing it is fine. Stats gives you more HP/MP to cast your spells.
Q: Why finish Frostmourne by lvl 20 then?
A: Mandatory. Your mana pool is big enough at this point, even if you can't hit any heroes, you never know what can happen. It also helps you farm faster. Frostmourne is a great ability to focus down enemy quick, and help chasing.
Q: Borrowed Time @ lvl 6, 11, 16?
A: I don't delay it because I like to use the death coil while borrowed time is activated. When Borrowed Time is level 1, there is a 30% chance that I mess up a heal attempt with death coil because the 3 second duration is too short. Instead of trying to heal myself, I hurt myself.
Q: Why RoB and not just a Sobi Mask, What about Void Stone?
A: RoB has an aura which helps your lane-mate and pushes. Sobi Mask is a cheap item to give bonus regen, it can be sold without losing much, Void Stone seems like a waste to sell if you need slots.
Q: How to I debuff myself when I am stunned?
A: You can't idiot, if your ally got stunned, and if you cast a shield on him, his stun/negative is gone instantly. You can remove other buff on yourself when you aren't disabled.
Q: I only play pubs, should I follow your guide?
A: This one is controversial, if tryhards are failing. I don't see a reason not to step it up and carry the team. If the carries are doing decent, try following what I recommended.