Describe the bug
Not so much a bug as an intended mod feature that does not fit with the pack,

Version of MC Eternal
Version 1.4.4

To Reproduce
Steps to reproduce the behavior:

1. Place desired blocks to duplicate in a circle
2. Throw "Hole Filler - Smart"
3. Wait for blocks to solidify.
4. ...
5. Profit

Expected behavior
Ignores non-ground blocks such as gravel, grass, etc.

fixed as of MCE 1.6, now that Hole Fillers is goned.

what the shit even

What the shit indeed. Very interesting bug / exploit! Works on all standard blocks but also things like machines so long as they are not multiblocks or pipes.