Tinder Sues Startup, “Kills Modern Love”

"tinder doesn't own 'n', 'd', and 'r'"

Can the argument be made that a dating app which is pronounced "threender" or "thrinder" could potentially confuse customers who might confuse it with tinder? Or worse, think it's an officially sanctioned nonconformist tinder?

IANAL, but yes - from wikipedia trademark page

"The law in most jurisdictions also allows the owner of a registered trademark to prevent unauthorized use of the mark in relation to products or services which are identical or "colourfully" similar to the "registered" products or services, and in certain cases, prevent use in relation to entirely dissimilar products or services. The test is always whether a consumer of the goods or services will be confused as to the identity of the source or origin"

To me, a consumer could definitely be confused by a name like that

Yeah, I could see that argument flying if people tell their friends that 3ndr is tinder for threesomes, which I suspect is part of their word-of-mouth marketing effort.

tinder didn't file for a trademark until 2015. and 3nder has filed or isn't registered yet. Not sure why both of them didn't file along time ago?

looks like tinder was first used in 2012 and 3nder didn't come along until 2014.