I had thought that Emacs’ C-t was mainly about correcting typos. It turns out to be extremely useful when working on Lisp macros which themselves write macros. This typically involves nested quasiquotation, where you can have multiple alternating sequences of open parentheses and backticks, or of commas, quotation marks and ampersats. While you’re working on it you often need to reorder these character sequences and C-t does a great job.