It's easy to simplify the matter of open defects, but it does depend on the circumstances. For example, your C550 port nav light goes in Rennes in the evening. Not Deferable, and you have no licenced engineer available under the approval of your 145 company to fix it, but there is an engineer there, with a spare, who can fix the problem, but wouldn't be able to sign it off. So what do you do?
a) Put it in the tech log, tell the pax the A/C is tech and go to the hotel.
b) Don't put it in the tech log, and fly anyway
c) Pay the local engineer a tenth of the price it will cost otherwise, and fly a serviceable aircraft.
Trouble is with using common sense in this business is that many abuse it.
I think Empty Cruise has a point though. If MX keep failing to rectify the problems, use the power of the pen!