Minecraft 1.13-pre7, Minecraft 1.13-pre8, Minecraft 1.13-pre9, Minecraft 1.13-pre10, Minecraft 1.13
In 1.13-pre6, changes were made to the fonts in Minecraft which affected obfuscated text.
Since 1.13-pre6, obfuscated text now uses a severely limited character set (looks like just the ASCII character set) whereas it previously used a rich character set of accents, letters, symbols, and other peculiar characters.
I have uploaded a video which shows the effect in 1.13-pre5 and 1.13-pre7. The video is at 25% normal speed but you can also view it frame-by-frame or test yourself.
On either version of Minecraft, enter:
This bug may also relate to
MC-132664, which covers obfuscated text not randomizing.