First, I'm sure the answer to this question is a definitive "no". Windows has never been able to natively mount Linux filesystems. But I ran into a strange thing today:
I created a container in VeraCrypt (improved TrueCrypt clone) in Linux, and formatted its' filesystem as EXT4. A container in this respect is essentially a disk contained within a file. My intent was to store files/directories in it that have characters that are not possible in Windows. VeraCrypt warned that mounting the container in Windows would result in Windows not being able to recognize the filesystem without a proper driver, and prompting to format.
So, I installed VC and Ext2Fsd in Windows. Then I mounted the container after authenticating. To my surprise, Windows immediately assigned a drive letter to the volume within the container, and the contents are plainly visible in Explorer. I even right-clicked the drive letter and went to Properties, Windows clearly lists the filesystem as EXT4.
At first I thought Ext2Fsd might have assigned a drive letter, but the container doesnt appear as a disk in either Ext2Fsd or Disk Management.
I'm baffled, how is this possible? The only explanation I can think of is that either Windows 8.1 has native EXT4 mounting abilities, or Ext2Fsd assigned a letter but isn't showing me anything. Can someone possibly follow my steps to see if this can be duplicated? Can you also try with only VC but without installing Ext2Fsd?
Edit: I'm tempted to think that this is the work of VC (as of v1.17 or earlier), that it somehow has a EXT4 driver built into it that Windows can access:
As an example I cannot assign a drive letter to my Fedora root volume in Disk Management (which is a real volume on a real disk, not a VC container), but I can manually assign a letter to it with Ext2Fsd (and it appears as a volume there along with the correct size), only then can I access the contents.
I thoroughly cleaned my PC of these 2 programs (both files and Registry), rebooted, then mounted the container in a portable copy of VeraCrypt. My PC was running in a so-called "shadow mode" via Shadow Defender, which is a software that transparently redirects all changes to a selected volume into RAM, any changes are gone after reboot. I got the same results outlined above, except this time Ext2Fsd wasn't present. The volume within the container doesn't appear in Disk Management, either as a disk or as a volume, and neither does the container, they also aren't listed in diskpart.