> I fail to see how praising the opponent differs from an ad hominem fallacy except in tone: addressing the interlocutor instead of the issue still fails to address the issue.

The ad hominem fallacy is meant to end discussion by attacking the interlocutor. This approach is meant to facilitate discussion by fostering a positive relationship with the interlocutor; the positive relationship is a means, not the end.

> addressing the interlocutor instead of the issue still fails to address the issue.

Logically, you are correct. Realistically, with a lot of people, failing to address the interlocutor will result in a failure to address the issue.

The "Let's keep personalities and egos out of this" methodology works in a rather narrow domain.