Bugs: should mostly be pretty easy to fix but a few are due to iOS system limitations we can't do much about (there isn't currently a way to install fallback fonts in a system-supplied button, e.g.)
You could just check if a character can be rendered before replacing the "Back" label with it or, if that sounds like an overkill (which it probably is), I think it'd be perfectly fine to keep the button labeled "Back" at all times. It'd actually work better in a way as when the label is replaced with just a single character, the area to tap on becomes very narrow and also, with the label width changing all the time (which moves the menu button as well) it makes it sort of confusing for the "muscle memory."
Features: we do have alphabetical sort order now, tap on the arrow icon at the top of Organize.
What I mean by alphabetical sort order is that for example "jùlí" (距離) should be after and not before "juānkuǎn" (捐款). There are probably some people used to the way it works now, so it could be a separate option under "Sort by."
The first benefit of an issue tracker (which could be made read-only) would be that people (such as myself) would not report some "known issues" just because they missed a forum post where it was already discussed. Although you generally tend to fix everything as soon as it is reported anyway, so perhaps this isn't good enough as the sole reason to go for it. But then you could track feature requests there as well and allow people to pledge some money towards what they want to see implemented, which would be a market-based way to prioritize feature requests. Anyway, just some food for thought.
Also, regarding startup times [...] if you're seeing slower iOS startups because of PQB files I'm inclined to think something else might be going on here - are your flashcards on iOS synced on iCloud?
On Android user dictionaries can sometimes load in the main thread, which is an issue that we'll be fixing shortly.
I shouldn't have written about both Android and iOS together, as there are probably different underlying factors at play. I have a pretty much legacy iOS device (iPad2,1) and despite this Pleco is still perfectly usable even with a few large user dictionaries and a lot of flashcards. just takes a couple of seconds to start up (even before I installed all these user dictionaries and flashcards though). If performance ever becomes a problem for me the obvious solution is to upgrade the hardware first. If you can make it launch faster then by all means please do but I shouldn't really be complaining.
On the other hand, on Android (where I have filesystem access) I noticed that the startup was instantaneous when I deleted all the PQB files but even having a single, empty "Pleco Flashcards.pqb" introduced a 2-3 second wait, so it's great to hear about the optimizations you're doing.
(For the record, I don't use iCloud sync. Would love to use a "Pleco Cloud", also syncable with Android.)
Thanks again!