I don't expect anyone to agree with me but still, I'll give you my opinion on it, it's unpopular one but here it is:I know plenty of people who receive communion/eucharist from both, why, well it's cause the effect is same. They both give you "energy charge", whether catholic or orthodox, they both give it, a strong spiritual fullfilling effect, not all can feel that though, requires certain senses to feel that I guess. Many of my friends who have certain jobs go between towns, cities and take part of both and no, they don't tell anyone about it.Theological part and opinions aside, the only person who makes this decision is you, and nobody else. If you truly want, then yes, you can take part of both, even if others do not agree with it and honestly, you don't have to explain it to anyone. I even know people who are part of either catholicism or orthodoxy and take the communion from protestant churches in areas where there is only one protestant church around. There is no point to argue over it, the choice is always yours, it will always be yours.Some folks spend a year going to one, the next year take part of another, then switch back, I know one guy like that.It's funny how you people make a big issue/problem out of this, the nature of this reddit section never ceases to surprise. The so called threat of being excommunicated would mean absolutely nothing to me, can always go to a different orthodox church. If I feel like then yes I go and take part of the mass and eucharist.I respect both of the religions and regularly use prayers of both orthodoxy and catholicism. To me they are both great and powerful religions and I love them equally. Like always, a personal message to OP.