[broadgage]

Many "proper" electricians dislike neon screwdrivers, except perhaps for doing up screws, and many employers in electrical or related trades forbid the use of neon screwdrivers.

However we must not become too paranoid, neon screwdrivers are simple, reasonably safe and reasonably reliable and fine for DIY or similar activities.
Any doubts about reliability may be answered by use of TWO neon screwdrivers, both of which have been proved to light on a known live source before the work.

A great deal depends on the size and complexity of the equipment being worked on the degree of risk.

Examples include; higher risk= high capacity industrial switchgear with a FLC of hundreds of amps and a prospective fault currents of tens of thousands of amps. Significant exposed metalwork that is live in use.
Before working on that, I would want FIRSTLY to observe it being isolated, removal of fuses in the substation for example, or isolation and earthing of the 11Kv into the transformer.
I would also observe that the power goes off ! Did the lights go out ?
THEN I would test with an approved tester, probably more than one tester.

Lower risk; replacing hall light switch for a neighbour. Turn off the main switch on the consumer unit and observe that the lights go out.
Use a neon screwdriver on the switch terminals as a "second line of defence", though in practice on a simple domestic installation, turning off the main switch and observing the lights going out would probably be sufficient.

Both the above are almost certainly the same voltage to earth, but have very different degrees of risk.