As per your request for a review here :)

CHEAT SHEET
+ Your notes for "Build Into" have Cutlass spelt wrong.
+ "Choose 2" allows poor choices. Warmog's and Randuin's? GA + Mercurial? I think you should break this up into "offense" and "defence" paths.
+ Thoughts on Zephyr?
+ Why max Tumble first?

GUIDE
+ "a movement / attack damage steroid." > Are you referring to Tumble? o.o
+ "Her skillset is aimed at having a passive laning phase" o.o I don't think this is what you mean. Her skillset is extremely aggressive.
+ Pros explanation is written poorly, in my honest opinion. It sounds jumbled up.
+ "very passive laner"?
+ This is the English teacher coming out of me, but "these glyps are outstanding" means nothing. "These glyphs are outstanding at fulfilling Vayne's MR needs" means something.
+ Instead of saying "xx is helpful", explain why it is helpful. What does 3 AD mean for Vayne? Put it into perspective for the reader.
+ "8% armor ignore"? :P
+ Flash isn't sneaky.
+ Last time I checked, Ignite ticks through Barrier, thus claiming Barrier doesn't get countered by Ignite is erroneous.
+ I wouldn't get Exhaust on Vayne.
+ "huge threat to your opponent, simple because"
+ "Visit Technical Play for an in-depth explanation." < make this linkable.
+ This is a small thing, but I consider it unprofessional to write words as symbols (&) in the middle of a proper paragraph.
+ Something I've noticed in your guide is the incredible amount of repetition. "Great for initiating a gank, immobilizing an opponent or for fleeing" + "Amazing for initiating a gank, immobilizing a target or for fleeing" = boring. If you're going to write a summary of the ability, don't repeat yourself in the "tldr" section.
+ "can also interrupt some dashes" > I do believe that other abilities have priority over Condemn. Technically you can't interrupt Bladesurge. If Irelia dives you, she dives you. You can always Condemn her away after, but not during her animation; in my experience.
+ A successful fully maxed Condemn does more damage than a fully maxed Silver Bolts proc.
+ I am truly disliking the repetitive nature of your guide. Everything "new" is already covered elsewhere. Think of rewriting aspects of your guide that are copy pasta.
+ "Not recommended to buy" > then why is it in the guide?
+ What about other boots? Enchantments? Elixirs?
+ I feel like you waste a lot of space with your synergy section.
+ With regards to both your synergy and opponent section, I'm not sure why you have such a long introduction. You end up repeating yourself about the champions you use as examples.
+ I've already told you about how I feel regarding your gameplay images. I think another reason I don't like them is the chosen text font.
+ I would not waste Condemn on a last hit.
+ Tumble reset works against all solid objects.

---

APPEARANCE (2.5/3)
+ I like the coding in your guide. A lot of it is very familiar to me, having seen it across MobaFire, or coded similar layouts myself. I especially enjoyed your colour scheme and how the monotony of the text was broken by relevant and aesthetically pleasing banners, icons and dividers. What brings your mark down for me is the gameplay images which are hard to read.

CONTENT (2/3)
+ A lot of your content seems like copy+paste. That was probably not intentional. I realise that is difficult to keep each chapter fresh and unique from the information before it. But by the 3rd or 4th time I read about Life Steal via runes/masteries/etc, I was sick of it. I was surprised to note that there didn't seem to be a certain "depth" to the guide as I was expecting. For instance, despite the repetitive nature of detailing to me the importance of why life steal is necessary on Vayne, you never mention WHY. I'm not exaggerating here, I reread the guide to see if you ever mentioned why life steal is so important on her. (maybe you don't know why?) From reading your guide, I feel as if you actually may not have a good working knowledge of Vayne. I mean this as respectfully as possible, but the guide seems shallow. It's got heaps of bells and whistles, but doesn't have the content I was expecting, especially when I think of your other guides, like your Udyr one.

VIABILITY (3.5/4)
+ I would definitely play Vayne the way you've outlined in your guide. I especially like the mastery choices, as they make particular sense for Vayne. What I didn't like was the item build paths in the cheat sheet. Pre-30s use this site and things need to be spelt out for them from the beginning (not multiple times throughout the guide). If you don't want to see Vayne's buying Boots, BotRK, PD, Warmog's, Mercurial's and Mallet, you need to be clearer by what you mean in the purchase order.

---

TOTAL = 8/10
+ I already upvoted your guide ages ago! Your guide is good. Better than the average MobaFire guide, by leaps and bounds in terms of viability and appearance. However, your content is lacking in my opinion. It may simply be neglect to link real knowledge with known knowledge; I know, for example, why attack speed is great on Vayne, but why isn't Shiv explained better? How can Shiv's passive benefit Vayne? According to your guide, Shiv's passive isn't as good as Phantom's. Is that true in all cases of every single game? Or, Last Whisper penetrates more armour than Black Cleaver. So? What does that MEAN? etc etc.

Off to uni, hope my review was helpful!
- jhoijhoi