Understanding the Etiquette of Greeting

In different Muslim societies when the day of 'Ashura (10th Muharram) is commemorated, a substantial number of people are clad in black clothes, and as advised by the Imams of the Ahl al-Bayt ('a), are overcome by sorrow. We are also told by Imam al-Sadiq ('a) to meet our people with the expression "May Allah magnify our reward due to our calamity because of what happened to Imam al-Husayn ('a)…" This however does in no way absolve us to greet or respond to the greeting of those who sincerely say "Salamun 'Alaikum". According to the strict Islamic Shari'a, whosoever among the Muslims greets you with peace then respond with a better greeting of peace or repeat the same (4:86). One who does not do so is religiously reprehensible and sinful as well. Don't we realize that on the very day of 'Ashura, we employ the same greeting for Abu 'Abdillah al-Husayn ('a), saying "Assalamu 'alayka yaa Aba 'Abdillah…" An innocent and sincere brother happened to meet one of my acquaintances on the day of 'Ashura, and when the latter greeted him with "Salamun 'Alaikum", instead of responding to the greeting, he loudly said "Azzamallahu Ujurana…" Indeed his intentions were undoubtedly pure, but his response was incorrect. He would have responded with 'Wa 'alaikum Salam…" and then have expressed his condolences "Azzamallahu…." which is highly recommended. In fact this is how we express our condolences to the Ahl al-Bayt ('a) in the well-known Ziyarat of Ta'ziya that we recite on Ashura Day. We first express salam "Asslamu 'alayka Yaa Rasulallah" (Peace be unto you O Messenger of Allah) and then continue with "Ahsana Allahu laka al-'Azaa' fi waladika al-Husayn" (May Allah grant you the best of consolation on [the loss of] your son Husayn). Notice "first salam" and then "condolences". It is important for us to understand the whyness and whatness of sorrow and express the same as it must be expressed. All the ambiguities clear out when we understand who are we missing and what are we missing him for?