Are SP or DP grid switches safest for 5A light sockets?

[JohnW2]

However, in other situations, it could surely be a 'problem'? ... for example, if one used the DP switch to isolate an appliance because one thought that its casing had become live - failure to interrupt the L would then surely be 'a problem', wouldn't it?

So the case has become live, but no RCD or overcurrent device has operated?

Indeed ... as would be the situation if there were no effective earthing of the case and an L-case fault arose. You might say that the requirement for two 'simultaneous faults' makes it 'vanishingly improbable', but the former of those 'faults' could have been present for years or decades without anyone knowing, so it only requires one 'new' fault.

However, as you know, I'm playing Devil's Advocate - since, as I've said, until the two recent threads here, I'd never heard this suggested as (or thought of it as) a downside of DP switching/isolation.

Kind Regards, John