Well, if one can listen to very robust and vigorous counter argumentation to one’s position and still hold that same position, then obviously it’s going to be far stronger and more solid (compared to circumstances where one blocks one’s ears to dissenting voices). And few things in this world are without their risks or shadow sides. Even if we think something on balance is going to be positive, IMO it’s still worth listening to some cautionary voices also.
The old role of Devil’s Advocate in the Catholic church comes to mind here. If some seemingly holy person was considered for sainthood, then a person would first be appointed to dig up all the dirt and try to find unsavoury aspects of the person in question and relentlessly make the case for why the person shouldn’t be declared a saint. Any positive decision would then obviously be a lot stronger (and sometimes it might turn out the original idea was not actually a good one at all).
There have been some good posts (on both sides). However, IMO there has been rather too much personalization in several of them. I think Ven. Analayo’s and Ajahn Bramali’s counter arguments to the recent Ajahn Thanissaro document are rather strong ones. That’s the core question. Analayo is actually taking rather a relatively conservative approach in working within the framework of the garudhammas. The argument is primarily a legalistic Vinaya one.
Most legal arguments are not black and white. Two sides put forward their most convincing arguments. Often the expected legal judgment of the court cannot be predicted in advance. Experts may hazard a guess as to the probability of success (70%:30%) or whatever. However, it ultimately will depend on the particular random of selection of judges on the day (and their particular individual varying philosophies or idiosyncrasies) to give a concrete decision, which often may as easily go one way or the other. The whole validity of single ordination question is a bit like that except that there won’t be any court to give final certainty (we no longer have the Buddha to ask).
I suppose there are three possibilities here on the pure legal question: single ordination is valid according to the Vinaya; single ordinary is invalid according to the Vinaya; or the validity is simply uncertain. Part of the problem with this argument is that this doesn’t appear to be clear-cut. In purely legal terms, the third option seems most likely to me. Then one has to rely on other non-legal types of arguments, which are a bit more subjective.
Even if validity is uncertain, different people will take different approaches. Some will think: this is good, it’s not explicitly ruled out, so why not just go ahead with this? Others more conservative in inclination will think: just because it’s not explicitly ruled out doesn’t mean it’s ruled in and do the benefits really outweigh the risks? Of course, many will not even agree that the question is uncertain. I find myself siding with the first (Analayo/Brahmali camp) rather than the second more conservative camp in this argument. Still, I think are some concerns worth listening to on the other side also. I also feel rather like @Metaphor that I’m a bit all too new to this (and maybe I’m being way too presumptuous in even commenting at all).