You'll need to make a custom unit based off Fountain of Life. Then add the abilities Life Regeneration Aura (Neutral) and Mana Regeneration Aura (Neutral). Make sure the abilities are custom so you can edit them.
Oh wtf, fountain of youth? Where you get that from...? Right out of thin air I hope, do you know how to use the Object Editor...? Cuz the way to restore hp can be many ways, but if your saying Dota's fountain at Sentinel/Scourge then that's Life Regeneration Aura (Neutral) and if you want mana, Mana Regeneration Aura (Neutral).
Ghan has said he has fixed this. Monovertex please confirm this fix. This was only a problem with people that had signatures in the upper levels like not the special members but the respected members.