Actually Rengeteki is not popular... or she gets totally no attention in Japanese touhou community.
She appears in Lotus Land Story of PC-98 platform. Most of Japanese touhou players have not played PC-98 touhou games.
We don't mention at tiny nameless fairly, and we know it for the first time by checking Touhou Wiki.
The name "Rengeteki" is a little bit odd for Japanese. We guess it is Chinese.
We are discussing why she is named "Rengeteki" in >>453->>461.
For now we guess Rengeteki is the character Taiwanese touhou fan made, but we have no source for it.
Japanese really don't know about Rengeteki.