Implicit string literal concatenation where
"string1" "string2"
becomes
"string1string2"
should be a language syntax error - not a feature.

This creates a silent error whenever someone builds a list of strings and forgets a comma.

I can't think of any good reason why the language supports this.  There are easier ways to build multi-line strings and there are already two explicit ways to do this on a single line.

It also violates the python principle:
"There should be one— and preferably only one —obvious way to do it"

I realize changing this might break someone's code.  If that is a large concern, maybe the interpreter could support an option to enable/disable support for this.

This is a long established language feature and is not going to change.  You could talk to one of the python linter projects about adding a lint option for detecting such; that would be the appropriate place for an option that would enable such checking.

Also, if you really want to pursue it as a language level discussion the appropriate forum would be python-ideas.  You might want to ask on python-list first about how it is used in practice, though, since it is used quite a bit (mostly in multiline expressions...so there might be an argument for doing something about non-multiline concatenation...that's the angle I'd take if you go to python-ideas with it).