When I went to Big Al's to get stronger meds for Lava last week the sale guy suggested I use Melafix. I said "No, he's a
betta and they cannot have Melafix". He said "Oh, it's a Betta, okay" I don't know if he really believed that Melafix was bad for labrynth fish but at least he didn't argue with me. I explained to him that Bettas, Gouramis and so on should not use Melafix and he said "Oh, okay, yeah". Hopefully if another Betta or Gourami parent asks for suggestions for meds he remembers that. Besides that Melafix is not a very strong med and I would not risk my fish's life on it even if it was safe. The few days wasted on a weak ineffective medication could mean death to the fish.
I too do not understand why people here or elsewhere insist on tempting fate and using Melafix in spite of people posting their own tragic experiences with it. It's not like it's the only choice they have. There are lots of other meds that are much stronger and safer.
I have the same problem with people who insist they can make an all female Betta tank work in spite of all the experiences to the contrary. They'd rather believe teenagers on other sites who set up a female Betta tank and post that everyone gets along (yeah for the first couple days maybe...) and then never follow up weeks later to say how many fish have been killed. I guess they feel too foolish but they are not doing any of the other female Bettas out there who'll suffer the same fate any favors.