How to connect to FTP from Finder with '@' in the credentials?
I personally am not surprised this is broken, but then again, I have larger faults with Finder's ftp implementation than this problem. From someone that's used to ftp on the command line, it's second nature to think of the @ as reserved to delineate the user part of the string with the host name part of the string, so perhaps that's a bug that the author of the code introduced.

Just as you're finding it hard to believe this is broken, I find it hard to believe Apple hasn't removed ftp from finder entirely and just pointed people to the Mac App store for a ftp client of their choosing at this point. Here's to hoping they do that for 10.9.

Assuming you are in need of a solution today, here are suggestions to work around it:


Try using ftp from the command line
Try to escape the @ with \ or otherwise trick the finder into getting past it as a delimiter
Use another program like Transmit that has more robust handling of any valid strings.
Searching the Mac App store in April 2013 yields no less than 56 choices for FTP.