IBM is also the reason MS-DOS doesn't support "-" for options and why it doesn't have devices in the "\DEV" directory on all drives. Support for "/" as path separator survived though!

Many MS folks used Xenix and were fans of Unix and very early DOS had SWITCHCHAR and AVAILDEV config.sys options for these things. But AFAIK IBM threw an absolute fit about it and forced their removal.

The DEV issue is specially annoying because DOS 1 didn't have directories - thus it could not have been much of a compatibility problem. But instead DOS/Windows is stuck being unable to support creating files named "CON" or "COM1" because it assumes device files exist in all directories.