What in particular about this method breaks correct token boundaries?
On my first read I read your comment as there are special tokens that require multiple tokens to emit, hence you can't get certain tokens emitted alone - but I don't think that's what you're getting at on a second read?
Interesting that you've found similarities between "d" and the hidden tokens for opening an xml tag, pressing caps lock and the other hidden tokens of note. I haven't run into any trouble extracting "d" tokens, is it a particular model that you see create that pattern?
I think the correct tokenization of the string will not have any tokens that contain mixed punctuation and letters, but the result of this approach does contain such claimed tokens.