Before I continue I think I should distinguish between (at least) three related topics.
1.) Is orthodox trinitarian theism true compared to any other metaphysic (theology or philosophy)? And/or is ortho-trin what is being testified to by scriptural witness (particularly and/or overall when the scriptures are systematically tallied up)?
This is not something I was bothering to argue, partly because this wasn’t what I was asked, and partly because even the metaphysical side of the question would take me 600+ pages to give a decent answer to. But mostly because I was replying to trinitarians whom, I suppose, already accept ortho-trin to be true and so who don’t have to be convinced of it. (Though they might have to be convinced of various technical details regarding it as a coherent set of theological doctrines.)
2.) Does ortho-trin lead to universalism and, if so, certainly or only suggestively so (and if only suggestively how suggestively)?
This is the question I was asked by Alex and (by proxy) Luke. This topic could be discussed con or pro by anyone whether or not they agreed ortho-trin is true: theoretically a unitarian (for example–whether Christian or Muslim for example!) could agree that God’s persistent action to save all sinners from sin follows logically as a consequence of ortho-trin, while still believing ortho-trin per se to be false.
Related to (2) as a subsidary issue is:
3.) Does ortho-trin have special connections to universalism that other metaphysical doctrine sets (such as unitarian or modalist Christianity in varieties thereof) do not have?
Although I wasn’t asked this question by Alex and (by proxy) Luke, I did bring up the topic several times in the process of discussing (2). This comparison, however, is still not the same thing as topic (1).
I mention this to caution that the topical focus of the thread is constantly veering off in the direction of (1) instead of primarily (2) and secondarily (3). As much as I love debating whether ortho-trin is true or not (whether exegetical testimony or metaphysics or both), this thread is really supposed to be an in-house discussion among trinitarians on the topic of universalism’s relationship to orthodox trinitarian theism.
On the other hand, it’s also true that topic (2) (and consequently (3)) cannot be discussed by anyone, trinitarian or otherwise, without getting a handle on, and an understanding of, ortho-trin (and to some degree its variations) as a doctrinal set. This is still not quite the same thing as topic (1), but obviously any attempt to do so (even by trinitarians) will tend to lean in that direction.
So I’m not putting my administrational… administerial… … alchemical… my foot down 
on the topical spread that has developed (and/or recommending other admins and mods in the thread do the same), but I am asking thread participants to please keep in mind what the focus of the thread is supposed to be, and try to keep aimed back in that direction even when drifting into (1).
This, by the way, in case anyone was wondering, is why I skipped over Paidion’s remarks about the subordination of the Son to the Father (including in GosJohn testimony)–though also because I had a lot of ‘work’ work developing at the office yesterday and needed to concentrate on that for the rest of the day (after which I was pretty wiped out. 
) That was purely topic (1); and, unlike his opening question to me which was also purely topic (1) he didn’t ask a question of me there (which I answered as shortly as possible in order to get back to the main topic).
Also, for what it’s worth, I’ve addressed his observations and arguments along that line already in multiple threads, to the effect that the authoritative and hierarchical subordination of the Son is no more a problem for ortho-trin than distinction of the Persons: the 2nd Person would certainly not be lying to call the 1st Person “the One True God”, and this in combination with the 2nd Person’s typical submittal to the 1st even in the single substantial ontological reality of the Deity (which by the way !!I discussed a lot in my main posts to Alex and Luke!!) means it would also be entirely proper, if strange to our ears, for the 2nd Person to call the 1st Person “My God”.
Obviously that situation can fit other theologies, too (though not every other theology–not modalism for example). I’m not disputing that. But since it is abundantly clear that Paidion for whatever reason either doesn’t remember or doesn’t care to remember what I have repeatedly said before along that line, so as to bring up the topic again in context of my replies already so that we can have an actual discussion on that topic, I saw (and still see) no particular reason to diverge from the topical focus of this thread to reply yet again on that sub-topic.
Although, being quite the baroque operator, I think I just did so again… But my point is that that kind of discussion is rather off-target for the topic of this thread anyway.
Consequently: there has been a large amount of discussion since I had to get busy elsewhere yesterday, but even though I want to address it all, I’m going to try to stay focused on topics (2) and (3). On the other hand, I do realize that understanding ortho-trin is important for discussing topics (2) and (3), so I intend to select some digressions into (1) where I think I can point the discussion back into (2) and (3). (Thus why I answered most of what I did answer from Paidion’s comment. 
And also thus why I went into some detail about what I have already answered in other threads in regard to the submittal of the Son personally and in utter loyalty to the Father earlier in this comment: because I thought of how that relates to my argument to fellow trinitarians in regard to establishing universalism as a corollary to ortho-trin!)
As the circle gets ever larger, the curve gets ever straighter. The curve of an infinitely large circle is in fact a straight line. Can a plane be enclosed by a straight line?