Oh, so you mean the sequence space-newline in a triple-quoted string?
Then yes, I can easily imagine a case where I’d want that - ''.join(multi_line_str.splitlines()) to format a long string that’s split into multiple lines for readability, but which wants to be one line for processing.
It may not be common, nor the only (not even the best, maybe) way of writing that. But it’s legitimate and working code that would be a false positive for this warning.
I could see them the same way I’d see trailing spaces in any other block of text, by highlighting the text and looking for highlighted spaces.
But more to the point, why would it matter that there were trailing spaces? Any possible problem that I can imagine being caused by those trailing spaces, I’d classify as a bug in the code consuming the block of text. After all, such code could just as easily be consuming text that came from some_path.read_text(), which could contain trailing whitespace on lines.