Not kosher
I'll bet the soldering idea isn't kosher with the Honda dealer, doesn't require enough parts and labor, or 'we just can't do that kind of stuff'. If mine ever did fail like that, knowing what the dealer repair proceedure is, I'll indeed just solder my own fix. If the burnt up connector wasn't obvious to the eye, then one could put out the word on the forum for assistance and myself or one of the many who have the electrical book for the Insight will gladly I.D. the connector and terminal required to make the permanent fix. 8)
The dealer recall on mine required the tech to replace the female harness connector along with the 'multi-function' switch for the lights/turn signals, and the kit had this little cheepo plastic tool to probe / disconnect the wire terminals out of the plastic connector. The re-ocurrance of this problem could very well be the manual labor involved with this proceedure. If the tech had a difficulty with the 'tool' provided, and started 'helping' the terminals in / out the result might well be the looseness problem was just transferred to the new connector blocks. Similar issues happend on Saturns I used to work on, but when I did them I made sure the loose problem was Gone, as 'comebacks are free' in the flat rate pay world of car techs.