I tried to reproduce this bug with links 2.1 as you asked. First of all, I found out that there is "Use passive FTP" option in Setup->Network options->FTP options. I have chosen that one. The easiest way for me to use a proxy was connecting my phone and using "localhost:8080" as proxy. I set the proxy in Setup->Network options->Proxies and tried to access some ftp servers (including ftp.debian.org). It worked even with "Connect only with proxies or Socks" option.
Though links documentation, which is accessible in Help menu or http://links.sourceforge.net/#man , is still in version 0.82, which means that it is normal that the manual doesn't mention passive FTP. --- I was running Debian 5.0.7 (lenny) with Linux Kernel 2.6.26-2-686. Versions of the packages are: sh-3.2$ dpkg -l | egrep 'links|libc6|libgpm2|libssl0.9.8|zlib1g' ii libc6 2.7-18lenny6 GNU C Library: Shared libraries ii libc6-dev 2.7-18lenny6 GNU C Library: Development Libraries and Hea ii libc6-i686 2.7-18lenny6 GNU C Library: Shared libraries [i686 optimi ii libgpm2 1.20.4-3.1 General Purpose Mouse - shared library ii libssl0.9.8 0.9.8g-15+lenny9 SSL shared libraries ii links 2.1pre37-1.1 Web browser running in text mode ii zlib1g 1:1.2.3.3.dfsg-12 compression library - runtime --- Aras Ergus
