You should submit a bug report with a direct link to that post so they can see why it didn't embed. There are a few instances where it doesn't so they should be aware of them all to fix them. Also tell them how you posted it. Pasted from what browser, etc.
Use the name Lindy for example. If I want to tag Lindy, I type it, and he is the first example because his name is exactly what I typed. It should be highlighted so I can just hit enter and it tags. However nothing is highlighted so I have to use the mouse to select. Hitting enter does nothing. Yes we are supposed to select who we want to tag, but when you type it exactly it should be selected. If you don't want that one, as in the name is longer and there are more selections, select another. FB works this way and it is very efficient. If it is the only one available, hitting enter should definitely work. But it doesn't. Also when you have a list of a lot of people, on other sites, you can put a space after the name and it shows that name. For example. I type Lindy(space). This would show Lindy and not any name like lindy773773 because you put the space. However in this case it is only showing a name that actually has the space, and not Lindy. It should show both of those.
If you tag a member in a post in sentence form (word, tagged member, word) and go to My Activity, in the teaser, there is an extra space after the tag. So tagged member, space, space, word. Activity Stream also.
Click a filter or time period in New Content and you wait 5 seconds for it to process. If switching filters this is a real pain. Takes forever. Also on mobile once you click a filter the menu closes but multi-select is possible so it should stay open, and needs a close button. Also the multi-select should be rethought in general. A lot of those combos don't make sense and some are not possible. PS. Tested on this site (IPS). Thanks
But if the editor contents is exactly what gets posted, then it is not WAI, because you (IPS) said this is the reason you removed post preview. It works in the editor, and is removed from the post. But it is supposed to post exactly as seen in editor per IPS.