[/B]Why am I here? Because it's a forum, mate. Open invite.

It's also a topic I find interesting, mostly because I think truth is a thing worth searching after. I'm also interested in trying to moderate people's positions when they're being incredibly dogmatic on an issue that doesn't need to have that position taken.
TBH, every time you say the issue is 'beyond debate', that 'no one' questions the long ending, when you make erroneous judgements of people, and when you simply misrepresent what a lot of bright and godly evangelical scholars have to say on the issue, I feel that's just more reason to continue the discussion. As Christians, we should be more interested in actually discussing issues of truth and reality reasonably than we are simply defending our own position. More interested in representing what people say and think accurately rather than whitewashing everything at all costs. And the FACT of the matter is simply that this issue is neither as critical nor as clear cut as you're trying to make it out to be, and it's by no means a marker for a bible-based evangelical faith.
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I see what you are proposing - that the 9-20 ending was lost very early, but was retrieved by the end of the second century in at least some manuscripts (enoguh to be referenced by Irenaeus), but lost in the two extant codices dating from the next century, and, according to the likes of Eusebius and Jerome, a great many other Greek texts of Mark in the century after that. It's certainly a possibility of some sort, in that it theoretically could happen like that, but I'm not sure why this is inherently more logical or plausible than the theory a v.8 ending was original. Happy for you to explain in more detail how you think that happened, because I'm not seeing the logic at this point.
The problem is this: Irenaeus is the only second century father that seems to specifically reference a part of the Long Ending as part of the text. This is not overly surprising, as almost everyone accepts that 9-20 is a very early addition (by very early, we are talking the better part of 200 years after the original). However, other early fathers do not reference it. Later fathers do reference it in the context of pointing out that large numbers of copies differ over whether the ending is genuine or not (Eusebius and Jerome specifically state they don't think those verses are genuine).
Others often put up the likes of Tertullian or Justin Marty as evidence for the Long Ending, but in almost every case they are either not quoting anything but making general references (that are too far from quotations of the text, or that coupld be applied to other texts), or the specific wording makes it far more likely they are (as we would expect of Latin fathers) using Latin texts rather than Greek texts, which already puts us a whole step away from what the original Greek texts said. And, of course, all patristic evidence is hampered by the fact that it is far harder to establish critical editions of the patristics than Scripture. Off the top of my head, I believe the earliest witness we have to Tertullian is the 12th century. The writings of the fathers have the same problem as the Scriptures (we don't have the originals), except the problem is even larger.
But the point, again, is to work out what is more likely: that it was lost, removed, or added. That it was lost is very difficult to believe, as it would have to either be lost within a copy of the original to have caused the widespread absence we see in large portions of the evidence, or it would have to be lost simultaneously in a large number of copies.
Deliberate removal is also far from likely - why jettison the whole portion of text, a whole 12 verses, something unprecedented in the whole study of biblical textual criticism? Why jettison the resurrection from Mark entirely? If you had issues with certain parts (e.g. snake and poison), why not just redact those portions? Why lose the whole block of text and end at v.8, of all places?
But you are correct to say that most copies of the NT contain the passage, either just 9-20, or with the alternate short ending, or with some sort of critical disclaimer. It's more than 95% of all the extant texts we have. But that doesn't mean a lot when most of those are at least a millenium from the autographs. A raw percentage achieves little in these matters, for obvious reasons.
Fixed