Answer
In the name of Allah, be advised, brother, that the Imams (PBUH) have ordered us to commemorate the tragedy of Karbala with all means possible. It is known that the commemoration of every occasion in every region and every sect is to be in a way that belongs to its people. In addition, it should not be in contradiction to any way in the Sharia. Lightening the candles on the days of grief has been old habits of Shiites. In some respectable houses, they extinguish the light to make the place dark, to remind them of the darkness that the Prophet (PBUH&HF) lived on the eleventh night of Muharram after the tents were burned and there was no light, no moon, no sun, and no other way. These candles that we see in Karbala have been burning for a long time even after the coming of electrification where the municipal used to quench street lamps, especially in the camp area to replace the darkness, and the families used to take their children to the camp to remember the situation of children of the Prophetโs (PBUH&HF) family.
Moreover, as long as the intention is a good one which is to commemorate that tragedy and Islam does not prevent this act, it continues and the one who practices it shall have rewards because it complies with the order of tragedy. Furthermore, we should know that all the communities in the world take their familiar ways of reviving the events that have passed on these sects. The Christians, for instance, every year embodies the crucifixion of Christ and others, as they believe that the religion of Christianity and the religious ones experienced such circumstances. We find no intellectuals like you denouncing this. I am surprised by your surprise at this, though we believe that Christ has not been crucified and has not been killed, however there are many customs of communities throughout the world that are going on like this. So, my son let the Shiites commemorate the tragedy of Karbala in every way that is not prohibited by Islam. Allah is the all-Guide and Helper.