Who's This? The somewhat generic sidekick hero in Who's Who Update '87 #4, page 29.
anti-drug animated TV ad that coincided with this campaign also couldn't use Robin, who was otherwise a member of the Super-Friends (in case the Titans tested well enough to go to series). The Protector appeared in all three "drug issues", and almost nowhere else. This issue of Who's Who Update confirms he was a member of the team at some point, though fans wouldn't be blamed for mistrusting his canonicity.
How you could have heard of him: He's had silent cameos in Teen Titans Secret Files #2 and the Infinite Crisis collection, but his biggest roles have been outside canon. He turned out to be one of Diah H-er Robby Reed's identities in Teen Titans Go #52 (a reappearance in #55 goes unexplained, however), and appeared besides in Tiny Titans #46, amusingly, as Robin's replacement.
Example story: The New Teen Titans "Drug Awareness" #2 (1983) "Battle!" by Marv Wolfman, Ross Andru and Joe Giella
Makes me think Jason Hart would be an interesting Titan to include in an official line-up. He would be the guy who'd have a very personal agenda, who'd drag the Titans into things they might not normally handle, and feel frustrated when taken away from his fight. The other Titans might even consider him holier-than-thou, leading to an interesting dynamic.
Who's Next? Moving on to the next issue... and beyonnnnnnd!