When I started messing about with bikes aged 14 someone told me to do that, so I did. They were very mechanically able in my eyes back then, so I never really given it much thought.
Back then the £50 heap of scrap metal bikes we rode needed repairing every single day lol, and never snapped a plug like this.
When I changed the SV plugs I did 1/4 turn iirc. That was the first time I'd touched plugs in over 10 years!
Of course, that doesnt mean it's right, and juding by your post it most proably isnt
