In the video clip, I compare the behavior of Rotate and Mirror and show that there is an issue with Left and Right Shift behavior for the Mirror/Inverse Mirror pair when placing single buildings in addition to the left/right key issues.
00:13-00:20 | F key | Flips Vertically as expected when placing blueprint
00:26-00:35 | L-Shift + F key | Flips Horizontally as expected when placing blueprint
00:45-00:52 | R-Shift + F key | Flips Vertically when placing blueprint, opposite of what we expect (the inverse)
Here the R-Shift + F key acts as if we just pressed the F key.
00:57-00:1:04 | R key | Rotates Clockwise when placing blueprint
01:09-01:17 | L-Shift + R key | Rotates Counterclockwise as expected when placing blueprint
01:28 - 01:38 | R-Shift + R key | Rotates Clockwise when placing blueprint, opposite of what we expect (the inverse)
Here the R-Shift + R key acts as if we just pressed the R key.
01:57-02:04 | R-Shift + R key | Rotates Clockwise when placing a single building, opposite of what we expect (the inverse)
02:13-02:18 | L-Shift + R key | Rotates Counterclockwise as expected when placing single building
02:26-02:32 | R key | Rotates Clockwise as expected when placing single building
Here the R-Shift + R key acts as if we just pressed the R key.
02:40-02:46 | R-Shift + F key | Flips Vertically when placing single building, opposite of what we expect (the inverse)
02:51-03:09 | L-Shift + F key | Does nothing when placing a single building, this seems like a bug
03:17-03:22 | F key | Flips Vertically as expected when placing single building
Here the R-Shift + F key acts as if we just pressed the F key. But, more importantly, we are not able to Flip the building horizontally!
So, we are not able to "Inverse Mirror" when placing single buildings, this may or may not apply to other modifier hotkeys.
Note: I already made a suggestion for a toggle to address the L/R key differences, which is a separate issue.