However, is it sinful in God’s eyes and/or disrespectful in the Protestant/Catholic Churches’ eyes to do so?
I’m basically aiming towards, is this something you’d need to attend confession for doing or would this just result in a priest or minister admonishing you to not repeat it.
And if it is sinful, what type? Venial or mortal?
It’s mortal to skip a Mass, which seems a bit dramatic, but that’s total judgement on my end.
You, or I, are not permitted to pronounce a sin “mortal” or “venial”. This depends on the individual person, their intent, and the full individual facts of the situation. It is a judgment that can be made only by the priest in confession. Skipping Mass may or may not be mortal so you are wrong to say “It’s mortal to miss a Mass on Sunday”. The more correct statement would be that it is a serious matter to skip a Mass on Sunday without a good reason, and it MAY be mortal. That’s all you can say.
With respect to the Catholic receiving Protestant communion, the following considerations would apply:
- Who is the Catholic and what is the situation? For example, is this a minor who is made to accompany his Protestant parent to a Protestant service and expected to go to Communion? Is this a Catholic with a Protestant spouse, and the Protestant spouse expects the Catholic to go to Protestant service and receive Communion? Is this an ecumenical service? Is there some other situation in play like the person is about to go out on the battlefield in 2 minutes and the only clergy available is a Protestant minister?
- Does the Catholic know it’s wrong to receive Protestant communion?
- What were the Catholic’s motivations for receiving Protestant communion? E.g. to avoid getting in trouble with parents, or because they truly believe all communions are the same whether Protestant or Catholic, or are they thinking of joining the Protestant church, or did they not want to look bad in front of their Protestant friends?
If a Catholic did this, it would be a good idea to mention it in confession and explain the situation and get guidance from the priest. As you mention, a Catholic is not supposed to receive non-Catholic Communion.
Yes it is sinful “in God’s eyes”. Why would you think God has some other gauge for sin than that of the Catholic Church which is his own Church? It’s not like the Church says something’s a sin but God then steps in and gives you a free pass.
Yes, it is disrespectful to the Catholic Church for Catholics to go around receiving non-Catholic Communion, but the Church might recognize that there are some circumstances where it can’t be helped such as the situation of a minor and their parent, and other circumstances where the person received for whatever reason without intending disrespect. This doesn’t mean it’s okay to go do it but it means that the sin might be mitigated.
I have no idea if it’s disrespectful in the eyes of a “Protestant” church and it’s irrelevant to me as I don’t conform my behavior to make Protestant churches happy.