I've been a RPer for over a decade now and here are a couple that come to mind.

[b]The Deserter[/b]

RPer A makes a RP request thread (of a certain fandom, idea, etc) for RPer B to express interest and the two start plotting. After sharing ideas, the two agree to finally start what seems to be a promising RP. RPer A writes an good quality over quantity, starter and awaits excitingly for RPer B to reply so the RP can officially start. And so A waits and waits and waits before finally messaging B who either flat out ignores him or says how they are too busy at the moment to reply even though it's been close to a week since A started the RP.

More to the point; What is the purpose of expressing interest (whether you are the GM or the partner) in a RP only to never carry through? I'm mainly talking about 1/1 as if your partner drops out, your RP is done if you cannot replace them. It's just so frustrating and I've encountered it time after time again and again site to site. I'm currently dealing with it now, and while I'm open minded to my partners' personal life, I find it a bit rude and terribly frustrating that our RP has been sitting for almost 4 days untouched even after my partner gave promises to reply soon. I get sometimes stuff happens or come sup where we can only post from our phones, and how hard it can be to give a good quality post, I truly get that. However, that isn't an excuse to never reply to the RP. (In the events it's your only means of RPing for the time being, that is.) It's even MORE aggravating when they give you every excuse in the book yet you can clearly seem them online, replying to all their other RPs... like why? When your muse is so high for a certain type of RP and you finally have found a partner that in turn, doesn't deliver, it is the worst ever. It's like a little kid knowing they got the bike they've always wanted, but can't have it till their birthday that is months away. It's mental torture because it's so close yet so far away! I've always loved when a partner goes 3+ days without posting and either comes back to say "Sorry, I was away" or how they lacked a muse. That's all fine, but PLEASE tell me! It's just out of respect to tell your partner that you will be away for several days while if it is lack of muse, let's talk about it in the OOC. Instead I'm stuck sitting, wondering if my partner has dropped the RP or not.

[b]Filler Writing[/b]

Quality over quantity writing are both needed, but the player must handle them correctly. I'm someone who would much rather read a single, detailed paragraph of my partner's characters POV rather than 3 broken up paragraphs that focus's on small talk of side character activates, and meaningless chatter because that's when it becomes filler writing and I view it as an excuse to make it seem like you put a lot of thought into your reply when really, you just wasted my time going on an on about how your characters sister was busy making the breakfast that morning. 

That being said, I can enjoy quantity just as much as quality, but give me something good to read. Side characters are much needed to help progress a story, but instead of merely writing that Susie, your characters sister, was making breakfast that morning; maybe have Susie interact with other characters? 

[i]"Susie, Tom's sister, was busy making the breakfast as he walked down the stairs. Pots and pans boiling with yummy aroma's filled his nostrils as she greeted him with a smile and glass of orange juice. "Hey there, funny face. How did you sleep?" The brunette asked as she continued flipping the flapjacks. Susie was always one for cooking, something Tom was thankful for as he wasn't much of a cook."[/i]

No only did I clarify that Susie enjoyed cooking, but I was able to have Tom reflect on the matter while also mentioning how their surroundings smelled and giving slight insight on to Susie's looks via her hair. I didn't go on about how she was wearing an red dress under an kitchen apron because in the long run, it didn't matter and that's when it can become filler, to me at least. I know some writers and readers very much enjoy getting every detail down, but I can assure you someone like me will start to fall asleep if you devote a whole section to talk about Susie's looks and how her eyes were like "orbs of blue" 

The last thing I need to comment on in regards to this matter is don't let posting length hold you back. If someone gives you a good quality post of 3 paragraphs, but you honestly only feel the need to write one that would do it justice - That's OK! As is taking the reins to reply with 3 paragraphs to your partner's single paragraph in hopes of moving the story. Too many times (good quality or not) do I see writers getting in the habit of "I give what I get" and that's when your RP starts getting into trouble. Giving good single quality posts is fine, but that's all your RP is going to be - Short replies mainly of your characters POV. Don't be afraid to write other actions or state other ideas while also writing as other characters! Trust me, I love when someone really captures their characters thoughts and feelings, but if that's all you're giving me, Tom and Susie are still going to be in the kitchen 10 replies later because all you've done is wrote POV instead of trying to move the story along thus causing a standstill.

I feel better now.