As for the specific use of the figure in the Revelation, there can be no doubt that there is nothing constructive about it. It comes out of Jesus' mouth, is sharp and double-edged (although only in the first occurrence are edges mentioned) and wipes out enemies. The obvious intention in that identification is to highlight the power of Christ's word to destroy: as that sword slashes, it cuts both ways, deeply, and mortally. The word Christ speaks is a force capable of completely obliterating his enemies--can you say Muad'Dib!
When Isaiah uses the image, the double-edged aspect is not specified and the effect highlighted is constructive rather than destructive. The image is wrapped in a prophecy meant to convey something positive. As far as the Jews are concerned (that is the focus of the Isaian usage), the penetrating conviction of God's word, particularly in the mouth of Messiah, is a means of drawing the Jews back to God. If you think about it, that makes sense given that during those last seven years of history (i.e. the Tribulation) God's agenda for the Jews is not judgment, but redemption.
When we use an expression like "it cuts both ways," we are actually calling upon the imagery of the double-edged blade. We mean by it that some stratagem or argument has a reciprocating effect. We may cut by using it but will also be cut in doing so. Our argument makes a point, but subjects us to the same charge we were making against our opponent. Nothing this correlated can be associated with the image of the double-edged sword in Revelation. The sword in Jesus mouth one-sidedly blasts away all his enemies, and there is no blowback!
The pointiness of that sword is not the issue either. Other weapons could have been used more fittingly as a metaphor if penetration would have been what was being gotten at. The forte of the double-edged sword is maximal lethality for every movement of the arm. The use of this image in Revelation is not trying to say that Jesus' word can penetrate to the heart, but that his word of judgment is unrebuffable and fatal. This is not about conviction, it is about wrath, and the image is used consistently to convey such throughout the Apocalypse.