It was implemented as a band-aid "fix" to get the SBD printing again when we were already late in the boom/bust cycle and more SBDs circulating was the last thing we needed
I see how it might have appeared to be that, but it was in fact looked at very carefully by at least some of us as a general long-term improvement to the system (for much the same reasons that you support reverse conversions). It was also not late in any cycle when the concept was first discussed, as I'll cover later.
But it was done when we already had a massive over-supply of SBDs
Arguably this is entirely backwards, as a major overvaluation of SBD indicates not an oversupply but an undersupply. But we may be confusing the timing of the design and development process with the timing of the HF20 activation (the latter being significantly later than the former).
The SBD purges were already happenning
I'm pretty sure that SBD purges in fact did not happen until after the print rate change was already discussed/designed on github, implemented, and finally merged to the source tree and scheduled for HF20. Whether this had any causal effect on the market is purely speculation, but it certainly isn't correct to say that the the purges came before the decision to implement. (As I noted the concept had been discussed, among several ideas, for a number of months, going back almost to the very beginning of the second SBD pump in late 2017.)
opportunity to maximise the asymmetric trade that SBD was offering but you can call me a cynic if you like
Possibly (though I personally saw no evidence of that), but if so then justice has been served.
This may be true, as it is for reverse conversions and other options for modifying the peg mechanism. But you know as well as I that the "consensus" decision was made on this change much later than that - when the late cycle situation was well known.
This is semantics really. Again you know as well as I that a large portion of the demand has been coming from speculation and people trying to take advantage of the assymetrical trade. We had far more SBDs in circulation than the platform users actually needed (or wanted). I'd call this an oversupply.
You are giving the market far too much credit. This is the same market that irrationally bid the SBD up to $17 USD and has been in consistent decline for most of 2018....now you're saying market participants read the github proposals and are reacting to them before "consensus" is being formally reached?
I understand you are trying to deflect and neither of us can prove their case for why things happenned the way they did but you really do appear to be stretching here.
As far as a "final/official" decision, sure. But there was no significant objection to it afaik at the time it was implemented and merged in github (July 20 btw). As a practical matter, it was going to get deployed, the only question was when (which was mostly a function of the rest of the HF20 development cycle).
Even before July 20, it was @timcliff who implemented the code change and he didn't go ahead with doing so until he felt there was already a reasonable consensus in support of it. Maybe he has a better idea of that chronology.
And that speculation was driven by limited/low supply. You suggest allowing for reverse conversions as a source of additional supply, which I mostly support. Printing is another source (which I also support). Both more printing and reverse conversions are a deterrent to speculation, in both cases by holding more supply over the market.
Again, there was no real question about it getting deployed once it was implemented in the code base. There literally wasn't any discussion at all about removing it. None.
Of course, one can absolutely question the rationality of the market and whether people pay attention to github (or even upcoming hard fork/release announcements). But it is also the case that with a print cap, particularly a low one, market participants betting on SBD to pump are not necessarily irrational. Once printing stops, there is nothing short of a hard fork or a market crash to bring the price down.