Tractate Moed Katan - Chapter 3 - Mishnah 7 מועד קטן פרק ג׳ משנה ז׳

They do not rend [their clothes] or bare [their shoulders], or provide a meal [for the mourners] except for the relatives of the dead. And they do not provide a meal except on an upright couch. They do not bring [food] to the house of mourning on an [ornamental] tray, platter, or flat basket, but in plain baskets. And they do not say the mourners’ blessing during the festival. But they may stand in a row and comfort [the mourners] and [the mourners] may formally dismiss the community. Section one: When one heard that a close relative had died, one would rend whatever clothes they were wearing. Baring the shoulder was also a sign of mourning. The mourner was provided by the community with the first meal after the funeral. On Hol Hamoed only a close relative would perform these practices. Others would not. I should note that today only close relatives do these actions in any case. The circle of mourners was bigger in the Talmudic period. Section two: It was customary to overturn the bed during mourning and then sit on the bed as a sign of mourning. But one does not overturn the bed during Hol Hamoed. This practice fell into disuse sometime after the Talmudic period. Section three: This halakhah is true in all cases. When bringing food to the mourner, they should bring it in plain baskets. A source in the Talmud relates that originally people would use fancy silver and gold vessels, but poor people would be embarrassed that they could not afford such fancy funerals and mourning homes. As a response the rabbis decreed that everyone must bring in a simple vessel. The mourning home is not a place where one should be showing off one’s wealth. Section four: The mourners’ blessing was stated on return from burial. They would stand in a line and comfort the mourner with this blessing. It may have also been recited at other points as well. But it is a public sign of mourning and should not be done on Hol Hamoed. Section five: While the blessing is not recited on Hol Hamoed, burial is. Along with the burial, they may have the formal line of comforters that would accompany the mourners on their way home. The same goes true for the official words that the mourner seems to have said to the comforters, to allow them to go home without accompanying the mourner all the way home.