PTFE on olives or compression joint threads is a BODGE and a surveyor worth his / her salt might spot it one day and put a negative comment referring to non-professional plumbing on a house buyer's survey.
Balls...
Well, i was recently asked to look at the plumbing at a house my client was thinking of buying - just to give an overview, and although things looked generally ok, i noticed PTFE on the threads of the radiator valves compression joint with the pipe and I did point out that this indicated DIY or less than professional standard plumbing work, which might indicate other short cuts elsewhere in the house.