[gordonguthrie]

For an amateur, living at the fringes of both Europe and the Russian empire, I think the boy Zamenhof done good for the 19th century

[knolax]

He did good but not good enough for a true international language.

[gordonguthrie]

Except a couple of million speak it - to a degree - and it has been going organically for over a century and shows no sign of dying

[knolax]

So only around ~1/8000 of the people who need to speak it actually speak it. It doesn't show any signs of dying but it doesn't show any signs of growth either.

[rikroots]

Zamenhof's Esperanto - it always felt a bit too, well, earnest in its aspirations to me.

If we're talking about universal communication systems, then my favourite will always be SolReSol - https://en.wikipedia.org/wiki/Solresol

[Note: I don't speak a word of either conlang]