People who do this are generally trying to be polite by not jumping right into the request, like one would in person or on the phone - and that’s great!. But text chat is neither of those things. For most people, typing is much slower than talking. So despite best intentions, you’re actually just making the other person wait for you to phrase your question (which is kinda annoying).
Hello
Hey
How are you?
Fine thanks!
Can I ask you a question?
Just ask
Saw this YCH, do you want to comm together?
Ooh, looks great! Did you get a slot?
It's full now :/
It took 9 messages to get the answer with 2 days of delay due to time zone differences
The most effective method of asking the question? Just ask the question!
Hello, I hope you are well! I have a question, I see this artist just opened this YCH, do you want to comm together?
Hey, long time no see! looks great! gogogo
Messaged them now, which slot do you want?
Being succinct and effective does not have to be rude, it demonstrates respect for the other person's time.