On the instabuddy issue:
When I am not diving with my family, the majority of my dives are solo drift in Boynton Beach, FL. I always carry my own flag. I will occasionally take another diver or small group, especially if they are unfamiliar with the area, relatively inexperienced, or lack confidence. I give very explicit instructions before the dive that it is their responsibility to stay with me and to let me know if they will be ascending on the flag before the end of my dive. I swim quite slowly and steadily and it is very easy to stay with me. I don't mind if they want to take photos, I do myself sometimes, or try to hunt for lobster, but the rule of staying with me is unchanged. I'll still look around for them occasionally and am certainly willing to assist with problems, but the major responsibility is theirs. In almost 8 years, I have never lost a diver using this strategy. I will even ascend with another diver or group if I'm concerned about their ability. I can always continue my dive once they're safely on the surface for pick up.
About a year ago I took a young husband and wife on their 1st drift dives, only their 2nd dive trip after certification. The man did OK, the woman had a lot of problems. She was underweighted and couldn't descend, I got her some more weight. At the bottom, she immediately lost a weight pocket and started up, I retrieved the pocket, caught up with her, and replaced it. After all this, we had drifted a fair distance off the reef and had moderate swim back. A little later, her cylinder came out of her BC and I replaced it. The rest of the dive was uneventful. I decided to accompany them to the surface, then finished my dive. The second dive went much smoother and we ascended together as it was only about 10 or so minutes before I would have gone up myself. They thanked me several times for the help and we went our separate ways. The next day they went out with a different boat. They happened to pass me underwater with another pair on the second dive, vigorously waved at me and gave me a big OK. The husband was carrying the flag! We passed on the dock at the end of the day and they thanked me again, with big smiles on their faces. Sometimes, it's really worth it.