Kubuntu Linux 13.04 64bit, AMD Radeon HD 4670 graphics
Broken: 2.70 official release (2014-03-19, hash 19e627c)
Worked: 2.68a (2.68.0 r58536)
Short description of error
Knife tool in some situations (not rare) makes not just one vertex on edge, but two in same location with edge between them.
"Same location" - that is "remove doubles" fixes this.
Bug is clearly seen when "Subdivision Surface" is in use.
Exact steps for others to reproduce the error
Steps (dublicated in *.blend textblock):
- Select plane oblect and switch to EditMode (if not already).
- Make knife cut like at image below - hitting every edge, not just top and bottom.
- Hit Enter. Now you should have image like one in the bottom.