Whether or not to reply inline in emails, is something to disagree on.
When I write an email, I aim at producing a text with a beginning and an end, complete with greetings and other politeness forms. After all, if I meet a colleague at the coffee machine, I also greet politely before starting to discuss, and when leaving I greet again (said colleagues do the same). So why not do the same in email?
Now, when a colleague responds inline in an email, I end up reading my own words mixed with their answer, completely destroying any line of reasoning in both my original mail and their response. I rather see that they respond in multiple paragraphs, at the beginning of each they concisely summarise their understanding of my point that they refer to. This serves a great purpose: at least I can verify if the first communication (from me to them) went without noise.
Moreover, even though modern email readers attempt to give different colors to the old email text at different levels of indentation / quotation, inline answering produces an unreadable mess of voices and colours. As if we are all talking at the same time and interrupting each other at the same time.
It happens to me often that I miss comments that colleagues injected into my email to them.
Do not understand me wrong: this fashion of responding that I advocate does not at all have to produce very long emails. It can be as brief as: "Regarding your point about x, ...."
Now, how do I raise my colleagues without pointing them to this very stackexchange question, which is too lengthy to attach to any email and which would be a very arrogant thing to write to begin with ("Let me teach you some manners, because I have the authority to do so.")?