Personal belief is that unforgivable sin is one for which you have no remorse, no guilt feeling, hence no repentance, no contrition.
And the only way to have any of those feelings is to crawl to the "loving" eldurrs, give them second-by-second description of your sin, then somehow manage to weep and gnash your teeth. Then after they boot your butt out of the congregation you need to continue to show up for the mental abuse for at least a year, and eat your shit sandwich with a smile, then IF they let you back in you must continue to crawl and kiss ass for another only god knows how long. If you do not do all those things you must have committed the "unforgivable sin".
I guess the governing body's Bible does not contain John 3: 16