I am no programmer, and there might be a reason for such behavior, but i would expect that a knife tool at it's current state would work like a knife operation without a need to reactivate it after each confirmed cut.
Right now, it seems that a knife tool,when selected, is not activated. As i see it, it's functions are "turned on" after the first click, and "turn off" after cut confirmation (at least visually). I would suggest that they always be "on".
Can't imagine a situation where i would not want to see a place on a mesh where i'm going to cut).
Hope that helps somehow).
Thank you.

Strange. With debug on i barely was able to catch this bug.
With no debug it was 100% reproducable.
Used c9df453ce70b build for debugging.

With debug on. The last cut action was bugged.

My system at work: Windows 10 pro 64 bit. GTX 650ti.
System at home: Windows 10 pro 64 bit. GTX 1050ti.
Both have 8 gigs of ram.

A bug shows itself in the process, when you have not yet finished the cut with spacebar or enter key.
It repeats often, not 100% times though.
Been able to reproduce this bug on a different pc at work.

Hi! I checked the drivers they were up to date. In latest build 9dde3e42a7c5 loaded the factory settings. Had no bugged result on a default cube ( tried 10 times in a row, or so ). But then created a new plane, changed it`s position, entered the edit mode and the first cut was black. Every newly created plane had same result (at the most). First cut is black, second one is normal.