Great examples of how imperfect translations become "standards" of truth.
I would like to add a couple.
(KJV) Mat 5:39 "But I say unto you that ye resist not evil." and (KJV) Mat 6:13 "And lead us not into temptation, but deliver us from evil."
In both of these cases, the word "evil" is used as a proper name and means the "evil one" or Satan. The importance of this could be a topic for another discussion, but I think everyone understands the world of difference between not resisting crime and not resisting a criminal, or being rescued from crime as opposed to being rescued from a particular criminal.
(KJV) Mat 6:12 "And forgive us our debts as we forgive our debtors."
The verb to forgive in this case is known as the "historical present" and would be better translated as forgave rather than the present tense to forgive. This has an important implication in understanding God's mercy being conditional on our responsibility to do unto others as we would others do unto us: that we may not ask for forgiveness unless we have forgiven others. This is not at all the message that comes from using a simple present as KJV does.
This is of course tied with the Orthodox/Roman Catholics understanding that we may not hold a grudge and ask God's forgiveness for our sins.
These small semantic points along with your examples Cronos, such as the very essential one in your first example (Mat 5:48) "become" (future tense) rather than "be" (present tense), completely defeat the naive Protestant notion that the Bible is so simple and easy to comprehend something even a child can understand.
It also illustrates how those who go through life trusting their own interpretation of the Scripture are making sure they never fully understand it.
Finally, this also shows that different versions of the Bible (redacted and re-edited by human hands and human minds) by necessity corrupt the original in meaning and content, even if not intentionally. One more reason not to all our trust in the Bible alone, as jo kus properly pointed out a few posts ago.
"Hail, thou that art highly favoured" (Luke 1:28) is sorely tendentious. "Kecharitomene" is a unique to Luke word formation from "charis", grace, and KJV elsewhere correctly uses "grace" to translate "charis". There are a few exceptions, but none in the Epistles of St. Paul where the theology of grace is defined. To translate "kecharitomene" as "highly favoured" tortured both the language and the meaning. St. Jerome's "gratia plena", "full of grace" is the only reasonable translation.
"that disciple took [Blessed Virgin Mary] unto his own home" extrapolates "home" without warrant. There is no "home" anywhere in the original, which says "eis ta idia", "to/with his own". Again, St. Jerome has it "in sua". It is possible that the King James translator wished to "correct" what seemed to him an incomplete sentence, but the result is that millions of Protestants are now misinformed of the last words of Christ. It is of course important, because adding "home" puts the adoption of St. John in a flat economic context, when the real meaning is adoption by Mary of the entire college of Christian disciples.
King James routinely translates "presbyteroi" as "elders". This purposely ignores "priests", which etymologically means the same thing, but came to be quite distinct from "seniors" or "ancients". St. Jerome, again, uses common sense translating "presbyteros" as either "seniorus", or "presbyteros", depending on context. Occasionally, King James's anticlericalism goes too far, as in "Is any sick among you? let him call for the elders of the church; and let them pray over him, anointing him with oil in the name of the Lord" (James 5:14). Now, what do you call a man who comes to the sick, prays, annoints and calls on the Lord? Answer: an old man.
These three errors have crept into every English Protestant translation of the Bible, so all of them should be avoided. Those of Protestant persuasion should instead read Douay-Rheims and when their eyes wander over the books Luther banned, piously avert their eyes.