They did have the code owners' name in nice formatted comments but they don't do that anymore, at least not in the Excel codebase. There are plenty of artifacts with the code owners names left behind (many having since moved on from Excel and Microsoft).
Mr Spolsky was a program manager, so I doubt he wrote much if any code that made it into the Excel binaries, but I'm interested to know if he did.
His name doesn't appear in either the Excel 97 flight simulator monolith credits, or the Excel 2000 "dev hunter" driving game, so he may have joined the Excel team after that, or they may not have been exhaustive lists.
They're still very cool ways to put developer credits into enterprise software :-)
Version control systems are better these days, so you don't need to. Even us C programmers have stopped putting names, dates, revisions numbers and other gunk in the comments.
You'd think his name would be everywhere on the internals.