I wouldn't call Locarno an irredeemable character at all. Heck, just compare him to Picard in the First Duty. They are eerily similar, and Picard admits he was brash in his youth and made some sort of similar mistake that nearly got him kicked out.
Locarno saw potential in Wesley and went out of his way to take him under his wing and accept him into Nova squardron when there were older, more experienced classmen wanting men. Whereas, Picard saw potential in Wesley and went out of his way to take him under his wing and made him an acting Ensign on the Enterprise, when there were older, more experienced officers wanting the job.
When confronted with the accident and the coverup, Picard gives Wesley a stirring speech about duty and honor to convince him to do the right thing. Lacarno gives Wesley a stirring speech about loyalty to your friends and the team to convince him to stand with them.
Picard was a young womanizing hotshot in his own words with no sense and without a shred of discipline, durin his youth. Locarno was a young hotshot who wanted to graduate a legend and "win" above all else.
Locarno fell on his sword once the truth came out to save the rest of the team. Picard took Sito(and maybe the other girl, it's a big ship) under his wing to make sure she was given a fair chance and what she did wasn't held against her.
So, there you have it. If you think Locarno is an irredeemable character, then I guess young brash Ensign Picard was too. Heck, after his screw up at the Academy that nearly got him expelled it still took him taking a Nausican knife through the chest to teach him some restraint and sense.