While routing the 108 Star Speedrun of this game I came across some new info for a few of the characters. Some are just really minor corrections, but having Dongo definitively figured out is nice info to have. Enjoy:
Dongo:
*You only need to give him one hammer total, though it has to at least be the Silver one from Sable.
*Step 1 - Sharpen a character weapon in your active party one time (doesn't matter if it's even Level 1 to Level 2), then back out of the menu and ask him to join you.
*Step 2 - Sharpen a character weapon in your active party to Level 12, then back out of the menu and ask him to join you again. The character you are sharpening must be in your active party. If they are in your Entourage this will not work. Step 1 and Step 2 can be done back to back.
*If you defend the Castle and Roy dies, you will need to bring Wabon with you in order to recruit him. Because Wabon is so elusive, the only time you can do this is after Stormfist.
*If you abandon the Castle, you can add Wabon in your party and get Dongo on the way to Gordius. If you don't do this, you will have to wait until after Stormfist to bring Wabon to recruit him.
*You cannot recruit him during the event where you have to go back to Dwarf Camp to fight the Assassins and head to Sauronix.
*If you want to get Dongo before this, just get the Silver Hammer from Sable and follow the sharpening instructions above, though as mentioned, you have to do this before triggering the event where you go back to the Dwarf Camp. Wabon is actually in the tent directly south of Dongo before he is recruited, which is why you can get him at this point.
Sairoh:
*One small update here, you don't have to buy Salt before the price skyrockets, and you don't have to make money when you sell it. Just to experiment, I didn't buy any Salt, waited for the price to skyrocket (which is the base price x6), bought 6 Salt at Beaver Lodge (3rd highest base Salt price) at $1620 each, then went back to sell it at Raftfleet at $600 each. This works just fine. Just remember to get the Salt dialogue from Sairoh before actually selling your Salt, otherwise it's like it never happened.
Murad:
*You only need to ask Murad to join you 3 times, not 4.
*Also, Murad can be found one final time in Stormfist after the late game events there. He is near the intersection to the right of the Inn and can still be recruited.
Haleth:
*You'll need to talk to him twice in Hershville before triggering the scene with Logg in the Castle Tavern. He is no longer there after the battle at Stormfist.
Raven:
*It's implied that recruiting Egbert is required before starting the quest with Solis in the guide, which is true (though he can be found in your Tavern later in the game when he moves from your Inn). Taylor, Marina, Belcoot, Oboro, Shigure, and Fuyo are also required to be recruited beforehand, otherwise Solis will not trigger the start of this quest.
Retso / Shun Min / Subala:
*I can confirm you do not need to talk to Retso about the Strange Fish in order to catch one. Interesting note though, he will still mention the Strange Fish even if you haven't recruited Subala.
*Never say never, but I personally have never caught a Strange Fish in any of the alternate fishing mini-games that Subala has. There is one version where you catch the most total fish (weight not important), and another version where only the single biggest catch matters. If you get either of these versions, you can cancel the game with the Square button and try again right away. Speaking of cancelling though, if you catch a Strange Fish and cancel out of the game, you do not get to keep it. You won't get the Strange Fish dialogue from Subala, and even if you go back to Retso, he won't recognize that you caught one. Obviously, it won't be in your inventory either.
*Most of the time, the game is free to win, however, Subala has put up over 500 on me more than once. So, she can go off when she wants to. In my experience, stick to the small and medium size fish, as the bigger fish almost always end up as ? Items or Boots.
*The Strange Fish can be any of the fish sizes in the game, but given that the larger looking fish tend to be items, you have a better chance of getting one while aiming for one of the smaller fish.
Eresh:
*You do not need to bring Jeane with you in order to have Eresh join you.
Sorensen & Babbage:
*Not really a correction, but an optimization. After finishing the Revolving Bridge quest, you don't need to go back to Estrise (and then to your Gear Room, back to Babbage's Workshop, and then back to your Gear Room again). You can just dump them both off in your Castle Gear Room, leave the Castle, and come back. They will both join at the same time. This just needs to be done after Lym's Coronation.
Alhazred:
*If you missed starting his quest in Rainwall, you can start the quest later in Estrise by the Trading Post (east of the dock on the north side of town).
*Also, you technically don't need to sleep at Marina's Inn to get your Cursed Book back, you just need to leave the Castle and return.
Killey:
*The guide mentions an unverified claim that you can get him without letting him out of Agate Prison, finishing Twilight Ruins, then going back there afterword to get him. This is not true.
Norma & Ernst:
*You can talk to her early on in Raftfleet (such as when you recruit Wilhelm and Mueller). You do not need to recruit Levi, talk to her without him, then go back and talk to her again. Just talk to her early on, then again after getting Levi with him in your group and you'll get them both.
Oboro:
*The info is correct, though it's worth noting that you can start the quest early on in Rainwall, bail on it after a few dialogue choices, and get him earlier than you would have if you skipped the quest altogether. Basically Oboro operates on a "points system" similar to affection points for other characters (Zegai). You can choose Option 2: "I'll go too!" after leaving the Inn for 1 point, then Option 2: "I want to see how this unfolds." for another point after seeing the shady character near the dock, then bail on the quest when you're asked to continue in his ship. If you get the 3rd Oboro point, you must finish the quest, which involves going all the way to Lordlake and back, fighting the Barows Soldiers at the Southern Wharf.
A few final notes. Whenever a recruitable character is following you on the map screen, you won't be able to recruit any other character that would also be following you on the map screen. However, you can still recruit some other characters, assuming you're not in the middle of a plot event where some are unavailable. Subala, for example, comes and goes in Raftfleet more than any other recruitable character during the story; sometimes she's there, sometimes she's not. I'm assuming because she transports you back to the Castle Dock to play her fishing mini game that might have otherwise messed up the games progression. You also can't do both of Euram's sidequests at the same time. Once you've started the Book of Condemnation sidequest with Alhazred, you won't be able to get Isabel and Mathias until you have completed it. The final cutoff point for recruitment is different for certain groups of characters. You can still safely recruit after Stormfist, though some people won't be available anymore.
Not related to recruitment, but a fun fact about the Champion Rune in this game. Richard is recruited at Prince's Level +10, so if you recruit Richard when Prince is Level 51, he'll be at 61. Throw the Champion Rune on him and avoid all random encounters. This works whether he's in your Active Party or Entourage.
Routing this game was fun and rewarding, infinitely more than Suikoden 3. I'll be doing more speedruns of it periodically over the next few months if anyone is interested, especially if you want to see how laughably easy the war battles really are.