I'm in India where the domestic supply is 250v @ 50Hz. I've been working - gradually replacing the solid-core wire/s with stranded wires purchased recently.
To my surprise the line tester showed a feeble glow when touched to a wire (no connections made i.e. both ends free) draped over the phase/live wire. That little piece of wire (about a metre in length) itself is new, and so is the phase/live.
Further, as a general precaution when I play with these things at the residence, I had taken the precaution of wrapping non-adhesive PVC over the phase wire. Ergo, insulation leakage really should not be an issue but I'm not possessed of a megger. Oh ... and the line tester glow dies when the supply is killed.
Assuming the insulation is fair - what could possibly cause the line tester to present a false positive? Could a static charge induced from handling be so strong as to cause a glow?