Just a quick chime in from someone who just recently strongly considered building a split junk rig. There tends to be passionate arguments in these forums when it comes to different types of rigs, especially when a lot of the authors of the rig "forks" are still active here - we have people who have focused hard on designing/building cambered sails, flat sails, flats with hinges, split junk rig, aerojunk, wingsails... Most of these derivatives have sought to improve on some points lacking in the others, so it's natural that whenever one of these rigs are brought up, usually touting their benefits, the weaker points would also be brought up along with the strong ones. This would be a terrible echo chamber if that wasn't the case! And the discussion here is generally very civil, unlike when trying to discuss junk rig on a generic sailing forum.
Some valid concerns about the SJR were brought up here, one being the excessive(?) balance of the rig, of which Slieve himself acknowledged initially when designing the rig for Poppy if I remember correctly, but he later turned confident in increasing it a bit further. There seems to be something specific going on with the slotted sail, because if you think about rigging a normal JR with 35% balance you would surely have some sheeting issues, which I know for a fact from what my dad has reported with his Arne-type cambered sail where he's been able to sail close-winded with the sheets slack, simply by easing the tack parrel to balance the sail across the mast. And anyone in their right mind would have to admit that not being able to feather a sail properly with ease is very bad for an otherwise seaworthy boat. The SJR is pushing these balance boundaries to the limit so there's no wonder there are (as there should be) some words of caution against it, especially when it comes to offshore use.
Secondly, another valid concern was raised regarding flapping jiblets. I have personally never seen an as lively flapping JR sail as on the SJR. Example in this video. This wear issue concerns both cambered as well as SJR sails, while it ignores flat (hinged/non-hinged) and wingsails. It's simply another thing that should be considered. David in this thread suggests adding battens, while Arne suggests tabling should be sufficient. I don't see how this is poisonous downplaying of the rig, while discussing offshore use - merely reasonable suggestions. I haven't seen Kurt Jon Ulmer on these forums lately but if he was asked about this topic I'm sure he would say that he'd happily live without these issues of all other rigs altogether and sail happily along with his non-flapping flat sail, which he used to point out in a lot of threads in the past. Someone new to JR would definitely get something to ponder out of that, instead of Kurt being downplayed as a hater.
Similarly, in the wingsail threads there are often downsides of the rig pointed out, like the lack of sail balance, the expense and labour involved in making the rig components. These are valid points as well, that should be brought up, if someone wants to build a wingsail. Likewise in a thread like this about SJR, different perspectives should have the ability to be brought up without scrutiny.
And lastly, is there a thread where David hasn't replied within 24 hours, offering help/advice/insight? :D This is what makes these forums so valuable, the number of knowledgeable regular posters sharing their knowledge for free.