From a priest reader:
Should (can) a Deacon assist at Mass if he does not intend to receive Holy Communion? I’m not sure.
The only person obliged to receive Holy Communion at Mass is the priest celebrant. He MUST receive.
I don’t know why it should be obligatory for a person not obliged to receive to receive.
(How often does one get to write a sentence like that.)
The role of the deacon is to serve the priest at the altar and read the Gospel. He can do that without receiving Communion.
In the Extraordinary Form Solemn Mass more often than not the deacon and subdeacon do not receive. Sometimes this is because they are priests and they have already said Mass. In the old days people were not permitted to receive Communion more than once per day.
It may be that someone could be concerned that it doesn’t “look good” if the deacon doesn’t receive. I can’t speak to that.
The most perfect form of active participation is the reception of Holy Communion in the state of grace. It is ideal that the sacred ministers receive, if they are permitted. Canon Law in the Latin Church says people can receive Communion twice in one day.
If a deacon doesn’t receive, I can’t see any reason to get my amice in a twist.