WinSCP strips UTF-8 byte-order-mask on upload during ascii/text mode transfers since version 4.1.
https://winscp.net/tracker/82
Though for FTP only since 5.0.8
https://winscp.net/tracker/888

You can prevent stripping by using binary transfer mode.
https://winscp.net/tracker/842

Option to disable stripping is tracked here:
https://winscp.net/tracker/842

Hello.

I updated my WinSCP from version 4 (I do not know the exact version, I didn't update everytime)
to version 5.1.2 (Build 2816).

The new version seems to break encoding of my files.

Copy/pasting over SMB or a remote desktop works fine, the server sends the file correct and umlauts display fine.
But uploading by FTP with WinSCP 5.1.2 the umlauts vanish and the file is 3 byte smaller than the original.

The files have been created with visual studio 2012.
Notepad2 says the original file is "UTF8 with signature"
After upload it only says "UTF8"

This did NOT happen with version 4.

I attached a screenshot, the original file and after uploading it.