After some testing, I'm thinking, that this is the better approach.
If I'm writing English text in a German wiki, I still should respect the the language specific quoting rules.
So if I copy paste "some text" from a wiki with global settings English into a wiki with global settings German ... It would change the visual representation of the English text in a way that imo is wrong.
If a tiddler with a \smartquotes pragma, is copied it could be done in the right way.
But the "per input" option would need to be hardcoded.
So my conclusion atm is, that we should have improved tools like FancyQuotes, that allow us to improve the writing experience and use the rules according to the language which is used.
Using the pragma with "text like this" would still be an option, if you want to keep the existing wikitext, but want "per tiddler" smart quotes.
There is one more problem with "rendered" smart quotes. If you copy paste the rendered text, the quotes are missing.
-mario