I don’t think it matters which quotation symbol you use but the main quote symbols must be different to the internal symbols.
so you could have …
“This is ‘my’ string”
‘This is “my” string’
Depending on which symbol you want to see in your final string.
Versions 6.5 to 22
Dell XPS- i7-6700 @ 3.4Ghz, 16GB ram, GeForce GTX 960 (2GB), Windows 10
Dell Precision M6800 - i7 4700MQ @ 2.40GHz, 16GB RAM, AMD FirePro M6100 (2GB), Windows 7 64bit