** Shares of dating application Grindr GRND.N falls 4.2% to $15.02 in early trading

** Ningi Research discloses short position in Grindr and says co's strategy boosts short-term revenue, but undermines platform's long-term sustainability

** "We believe Grindr's paying user numbers are inflated, its product is deteriorating, its user base is increasingly alienated, and its long-term prospects are deeply compromised," Ningi says

** Upto last close, shares down about 12% YTD

(Reporting by Anshi Sancheti)

((Anshi.Sancheti@thomsonreuters.com))