This kind of coding style leads to unmaintainable and unperformant code.
In my opinion, reads more easily as:
This coding style leads to unmaintainable and poorly performing code.
The key to well-written documentation and reports lies in ease of understanding. Adding poorly understood words such as performant decreases that ease.
In addressing the use of such a poorly described word as "performant", I came across the following lovely excerpt:
"The unlovely language of this unreal world floats along on a linguistic sea of rollouts, step changes, public domains, fit for purposes, stakeholder engagements, across the pieces, win-wins, level playing fields and going forwards," the report says.
I believe this wholeheartedly encapsulates the why's and wherefore's of not using vernacular that is imprecise, vague, and designed to confuse.
Sir Humphrey Appleby, in 1986, put it fairly succinctly when he stated:
‘Sometimes one is forced to consider the possibility that affairs are being conducted in a manner which, all things being considered and making all possible allowances is, not to put too fine a point on it, perhaps not entirely straightforward.’
See http://www.theguardian.com/society/joepublic/2009/nov/30/english-language-misuse and potentially, http://grammar.about.com/od/words/a/Doublespeak-Soft_Language-Gobbledygook.htm for more examples of why it is important to speak plainly and in a manner that allows ease of understanding.