The Sametime server I use requires 'Direct connection using TLS'. At least that is what the Sametime 7.5.1, Preferences, Server Communities, shows in the working native client. I think this is the problem. I don't know for sure. The error I get is: Connection Reset
Does anyone know how to set up Pidgin's XMPP client to get this to work? If not, how do I put in a feature request?
You can't use XMPP account type to connect to sametime servers
XMPP and Sametime are different protocols, you do not set up an XMPP account in pidgin to connect to a Sametime server, you set up a Sametime account in pidgin to do that.
Offhand, I do not know whether pidgin supports TLS connections for Sametime or not, but if you haven't been trying a Sametime account in pidgin you should and see if that works.
As to filing a bug report you do that at http://developer.pidgin.im/.