@ The Fall Guy: Good catch!
The Greek noun ekklhsia/ekklesia/ecclesia in its Biblical context, is indisputably understood by scholars across the spectrum. The word refers to a group called out together, a congregation or assembly of various size, from a small group of Christians meeting at a private home (Ro 16:5) to the collective members of the Christian "church" (1Co 12:28) Watch Tower well knows this, and has even published teaching to those same points.
So, it is a real leap for Watch Tower writers to imply that Jesus' words at St. Matthew 18:17 limit judicial authority and responsiblity to an elite few elder men within the larger ekklesia, because the Greek expressions for elders/older men/overseers are entirely different Greek nouns which do not appear anywhere in the context of that verse, but Watch Tower teaching, such as page 151 of Jesus - The Way, implies otherwise.
Watch Tower will defend its application of that verse by extrapolating a literal rendition of the Greek roots of ekklesia... "ek, meaning "out," and kaleo, meaning "call". Hence, it pertains to a group of persons called out or called together, either officially or unofficially." That is a quote from Watch Tower's book Insight volume 1, page 496. This is interpreted by Watch Tower to support a small group of appointed elder men being "called out" or "called together" from within the congregation (ekklesia) to exercise exclusive judicial authority over individual members of the same church. By design, that power structure is what then gives them a "scriptural basis" for excommunication by tribunal. Without this structure of hierarchy, such judicial decisions would be, by an unbiased reading of 18:17, the product of an essentially democratic process governed by the collective members of a congregation, which obviously would undermine the hierarchy establishment designed by Watch Tower to facilitate its policies of control and excommunication.