Turning to William Trollope's Analecta Theologica (1842 2nd ed.) Vol. 2, p. 87, we find the following breath of fresh air:
Trollope is to be appreciated for his insight into the reality behind the textual evidence, especially given the spotty knowledge available in his time, and the primitive state of textual criticism as a 'science'. The following modern footnotes clarify what was missing from view for Trollope and his contemporaries, but which is readily known to us today:
"The narrative of the Woman taken in Adultery, contained in the opening of this chapter [ch.8], together with the last verse of ch. 7, are wanting in a great number of the best MSS.  Many of those also, which retain the passage, mark it with obelisks, as an indication of supposed spuriousness;  and it exhibits a greater variety of readings than any other portion of the Scriptures whatsoever.  In some copies [family 1, 10th cent.] it is found at the end of the Gospel; in others, elsewhere[late copies], and in others, again, at the end of Luke 21 [fam. 13, 10th cent.]; Origen, Chrysostom, and Theophylact have taken no notice of it in their commentaries;  and it is first explained by Euthymius, a writer of the 12th century.  Many of the older versions are without it;  and several of the ablest critics have rejected it as spurious. 
Now Papias, in a fragment cited by Eusebius, relates a tradition respecting a woman who was accused of many crimes before our Lord, which was taken from the Apocryphal Gospel of the Nazarenes; and it has been thought that this was the legend in question, which has by some means found its way into the narrative of St. John. Others have thought that the incident is the relation of a real fact; but that it is one of those events in our Lord's ministry which were not inserted, for want of room, in any of the four canonical Gospels, though they were long preserved in the Church by oral tradition. (See Luke 1:1, John 20:30).Several of these histories were recorded in the margins of early copies, so that some of them at length obtained a place in the text; and it may not be impossible, from the remarkable variations in the MSS, that the preservation of this story is to be thus accounted for. (See on Matt. 20:28, Luke 6:1).The weight of the evidence however, both internal and external, unquestionably preponderates in favour of its authenticity. The majority of MSS are considerably on its side; and its absence from those in which it does not appear, is traced by Augustine (de Adult. Conjug. II.3) to a scrupulous fear, that the ignorant might be thereby induced to think lightly of the sin of adultery.
At the same time it is sufficiently evident, why Jesus thought proper to evade the question of the Scribes. A snare was laid for him similar to that which lurked in the insidious question respecting the tribute-money in Matt. 22:17. Had he countenanced the punishment of the woman, they would have accused him to the Romans of invading their judicial authority; and had he, on the other hand, referred them to the pro-consular tribunal, they would have held him up to popular hatred., as sanctioning an infringement of their liberties and rights. That he did not palliate the atrocity of the offence is evident from the caution with which he finally dismissed her. pro- Whitby, Lightfoot, Mill, A. Clarke, Michaelis, Kuinoel, Doddridge, &c. (con - Grotius, Beza, Le Clerc, Wetstein, Tittman, &c.) See also Horne's Introd. Vol. IV. p. 315.
1. The final count of extant MSS missing the passage is actually quite small. Some 1,350 MSS do have it, while only a few dozen have left it out.
2. From the thorough research of Dr. M. Robinson and others, it is now clear that all manuscripts containing such marks (obelisks, asterisks, archus and telos) are in fact very late. There are no early manuscripts containing the passage with such marks. The only early manuscript with a special mark, Codex B (4th cent.) does not actually have the passage, and there is some doubt as to whether this mark (a double horizontal dot, an 'umlaut') refers to the passage, or a textual problem in the preceding verse.
3. The alleged great number of variants in this passage is at best a guess, and no similar passage of John has ever been collated for comparison. (See our previous post on this). In any case, variants are an indication of copying errors subsequent to the existance of a passage, and have no bearing on authenticity.
4. Its now known that the early commentaries, specifically prepared for public reading in church services, don't comment on any passages which are not actually read to the congregation first during the service. Many passages were never publicly read during services, for instance the book of Revelation.
5. We now know that Didymus (c. 350 A.D.), an early popular Greek commentator, also cited this passage when commenting upon another O.T. passage. This disproves the theory that the passage was unknown and unquoted until the time of Euthymius (12th cent.).
6. Several of the ancient translations (e.g., Syriac, Coptic, Armenian) were not strictly continuous-text copies, but were ecclesiastical copies prepared for liturgical church worship. These versions follow early 'lectionary' practices, and exclude passages not read publicly in services.
7. Here Trollope, writing in 1840s, is referring to early critics and commentators, such as Wetstein and Grotius. Many of these people were anti-supernatural rationalists and skeptics, with heterodox doctrinal beliefs, and paranoid attitudes spawned from the violent and controntational early Reformation environment. Wetstein for instance, rejected all ancient Uncials, because he believed they were laced with "Latin" interpolations. Lachmann wrongly imagined that the traditional text (TR) originated in the late Middle Ages! Griesbach naively embraced the belief that older manuscripts were more accurate, because he did not fully comprehend the many independent lines of transmission in the Christian period.