"A hundred thousand welcomes friend, and cheers!"
Translation:Ceud mìle fàilte a charaid, agus slàinte!
"A charaid" is the vocative form of "caraid"--it's the form you use when you are actually speaking directly to someone. So if you were talking about your friend ("I said hello to a friend") you would use "caraid", but if you were addressing your friend directly ("Hello, friend!") you'd use "a charaid".
If you are offered some accents but not the one you want, change the language of the keyboard to the language you need or another one that has the same accents. Most English-language keyboards have the ones needed for Irish, Gaelic, French and Spanish, but if you are using a non-English keyboard, or you need a ŵ in Welsh, a ß in German or a ð in Icelandic you may be stuck.
Yes there are bugs in the system that the mods can do nothing about. The correct response is to file a bug report at https://support.duolingo.com/hc/en-us/requests/new but as we know from experience that they won't do anything, the only advice is to stop using the app, which has far more bugs, and more serious ones, than the website, which works pretty well even on a phone.
A house is not built in a week, my friend! It takes time to fix bugs, test the fix, and propagate the fixes! And sometimes the hardest part is finding someone to assign to do it, much like finding a plumber to fix a little leak. In any case, I think this one must be fixed by now, as I haven't seen it recently. And certainly reporting them on the link you gave, or via the little "report a problem" flag -> "Something else went wrong" is the correct thing to do.
I have answered this twice on this page already, once brief and simple, the other going through lots of similar words.
As for the desire for feedback, yes it would be really great if there were some system for putting in feedback apart from reading these discussions. It would be wonderful if you could hover your mouse over any word in the sentence and it could explain what is going on. But no one has done any development to the Duolingo system since it was first invented, so what we have is basically a very good first attempt.