'I seem to recall that candles are a reminder of the early church gatherings underground in the catacombs, or in back rooms and cellars of homes of believers, in the days before churches were allowed in the Roman empire. As you say, this tradition has continued through the ages in all catholic churches.'
I believe you are correct: candles are most likely remnants of catacombs and early home-churchs; that is, they probably found their origination there. Candles, however (like most sacramental realities), are multi-layered. The candles do serve as a simple, primal reminder of the catacombs, but candles also have meaning in so many other ways.
For one thing, candles are sources of light - they help us see, and they are embodied reminders of Christ, who is the Light of the world, as well as a reminder of the Triune God (in general) who gave us the blessing of light, who created it in His goodness.
Also, candles embody the reality of Jesus Christ's / God's love - one could say 'the Triune love', the love at the heart of reality that defines reality and gives reality its meaning. This love - agape, in the Greek - is a love that gives sacrificially and expends itself for the absolute good of the other with no concern for itself. Candles give us light at the celebration of the Sacred Mysteries, but they 'give up' themselves to do so; the wick and wax burn away to give us light. They're a subtle but powerful reminder of God's love for us.
. . . Candles can be used by anyone and are in themselves good things. I would even go so far as to say a protestant church service is edified by the use of candles, as this is at least a step back towards the source of protestantism in the first place; that is, one of the most notably embodied realities of the loss of meaning that is in fact protestantism is the empty, lifeless nave ('sanctuary') - no Tabernacle, no Christ candle, an empty Cross, etc. My point in the entry was that we miss the point completely if we elevate the use of candles to some sort of super-religious function to the exclusion of Sacred Tradition, within which organic reality the candles find their full meaning and location, and in which context they were first originally used.
-r
