I haven't read all of the thread yet (oy, my eyes, it's a long thread!) but, from what I have already seen, I agree completely with S_T's posts. (...bet you never would've guessed that, Yafet!
)
"Communion" was also the hardest and last thing for me to let go of in my stepping into Biblical Messianic Judaism: first my Catholic understanding of it, but also later, my protestant understanding (and acceptance) of the teaching as well.
As re: Catholic communion, and the concept of transubstantiation, I have a couple of links about the practice and its origins, which I can add to the thread too. Hopefully no one else has already given these links (and if so, my apologies for repeating them).
While not the most eloquent of pieces this one has some decent insights:
http://sxws.com/charis/apol8.htm
I can't link the article directly, for some reason, but if you click on "articles" on the left menu at this site, and then select "Do THIS in Remembrance of ME!" in the pull-down box that comes up, you'll get to an interesting article from a MJ perspective.
http://www.petahtikvah.com/
I would also like to mention an excellent point made to me by a Messianic woman whom I hold in very high regard. She pointed out that since it was against the Law for Jews to partake of blood, if Yeshua had meant for His literal blood to be drunk by Him and the disciples during the Last Supper, He would have been unclean because of it and He would have been unable to die having perfectly obeyed Torah. Since partaking of blood (and even flesh of a living thing, no?) would have been breaking the Torah, Yeshua was clearly not doing so in the meal, and never changed the bread and wine into His body and blood; it was symbolic, Pesach-related, as so many of you have been trying to make clear in this and the other discussion thread going on.
My other thoughts on it: since the atoning sacrifice had not yet been done by Yeshua, the price had not yet been paid... so the disciples were not partaking of an efficacious sacrifice in that Passover meal... and there would certainly be no point in Yeshua taking any of the bread and wine Himself, then, if it were in fact His very blood and flesh.