before i start answering, i did receive your clarifying question and i'm taking it into account~ but i think you were already clear so i'll just answer this here.

the answer is not clear cut, so i will start general and narrow specific: the -ie suffix is used out of fondness sometimes, it is not always a particle. people who try to use the particle as a reason to dismiss fondness between two people are not at all people that should speak with authority on the subject in my opinion.

i think in the peniel example, it is out of affection when they call out to him using hyung-ie. it's a way of being affectionate since 'hyung-ah' is very very babyish. not that i can be sure of anything, but i read it that way too.

in the han relaying the story about lee know short, i think it's a mix of fondness and force of habit. when referring to lee know like this (talking about him when he isn't there, in the third person) you need to use the ~ie particle a lot in your sentences, so i think it was just reflexive here rather than necessarily an innate fondness thing! though obviously han is very fond of lee know.

for the last one... i'm not the best person to explain this, because i don't study language for a living and can only speak from my experiences, but the more you listen to korean and learn it, there are times where, navigating by feel and instinct, a one-syllable (or one character) word needs a second syllable for the sentence to flow smoothly or to sound nicer. "uri hyung-ie" just sounds way nicer than "uri hyung" which feels very clipped when you say it aloud? so yeah, i think that one can also be attributed to more of a flow of sentence thing than a fondness alone thing.

i hope that this explanation made sense! i also encourage you to not read too much into ~ie in general. it's used for so many reasons that it's impossible most of the time to know why it was used, so in that sense, i don't think there's that much point to analyses of who uses it when and for what reason... there's so many other things to focus on when it comes to interpreting degrees of fondness and intimacy that have nothing to do with what particles are used, and arguments that hinge entirely on this particle in any one direction just aren't going to make a lot of sense.

thank you for your question! :)

all of these are relatively true! lino has talked before about how he doesn’t really think jisung should view him as a hyung when he’s more of a friend, so you see jisung dropping hyung with lino a fair amount, though it’s not all the time by any stretch. felix never uses hyung with chan in english, because that’s not something that would exist between them in australian culture, and they keep english pretty separate in some ways so that they keep practicing their accents and don’t lose them, etc. hyunjin and changbin have always had a lot of running jokes about the hyung distinction (changbin calls hyunjin hyung a fair amount when he wants to be babied by him, especially early on when he was not necessarily “hyung line” in the group), but i think hyunjin has dropped hyung more lately due to the fact that they’re using international age. it’ll be interesting to see if he picks back up again after changbin’s birthday or if he keeps the joke and modifies it! 🥰

hihi! so i’m not japanese, but i have read some scholarly articles on this terminology because i find the term ‘gap more’ to be a very useful shorthand. i’m going to paraphrase those papers here as best i can, but i totally encourage scholarly research on the term if you’re a nerd like me - it’s really engaging stuff!

basically, your research is correct, but it’s a slang term so it’s used in a broader context! when lino does x, it gives the stay moe (that affection blooming in their heart for his cute charms). moe is typically tied to unrealistic/fantasy ideals of purity and endearing qualities, so there’s a sense if you feel moe or a character has moe that you would like to protect them as a fan.

i hope that’s helpful!

usually, slang either sounds similar to the words it originated with, or combines the first character of each word, so you can guess them the bigger your vocabulary is! if my vocab isn't good enough or my brain isn't connecting the dots well for me that day (or it's a meme or something), generally a google or naver search depending on how niche i think it is. i try to read more than one thread if i can find them, usually one explaining in english and 1-2 explaining in korean. hinative is a decent starting point for when you can't find something on naver or any korean resources because your search terms are too broad or there's too much aegyo for them to have results, but it's not reliable to get answers from on its own. italki is generally better even though it's also basically crowdsourcing. openslang dictionary is difficult to filter but sometimes has things i can't find other places. koreanary is good to try if naver dictionary doesn't have it. if you search in korean you'll find more than one site that explains slang terms, but just like how urban dictionary has incorrect slang definitions, so too do those sites, so you usually should cross-reference a whole lot!