@Coises, after @PeterJones mentioned your posts and your issues, I read discussions and your explanations. First I’m impressed with how many details you have in mind and this and other questions are very important. Also I noticed that while many agree with your observations, there are not so many who are frustrated by this as much as you are. Maybe I’m in your camp here, at least partially :)
My two cents are related to the fact that my previous activities were heavily influenced by Borland-originated editors (for example, in Delphi) where Virtual Space (now in npp too) was always on by default (I’m not even sure whether it is possible to switch it off). Lazarus IDE editor is very similar since Lazarus/FreePascal was inspired by Delphi/Turbo Pascal). Amongst other things this mode basically treats trailing space as virtual space. I just made a test when I forced multiple spaces after some last non-space character and tested End (SCI_LINEENDWRAP) operation. In Delphi/Lazarus the caret goes after the last non-space symbol so if there are no added spaces at all. The selection with keys also mostly ignores these new spaces, I could not select it with any ctrl/shift arrows operation. In npp End (SCI_LINEENDWRAP) jumps to the end of the new space so it is obviously kept intact. With selection in npp it’s mixed. Shift-arrows act like virtual space is everywhere, but Ctrl-Shift-arrows (SCI_WORDRIGHTENDEXTEND) “feels” this new space. Anyway, I’d suggest that when Enable Virtual Space is on, trailing spaces might be treated with some relaxed rules, but I’m not sure npp is ready to implicitly get rid of spaces without the user asking for it.
As for non-Virtual Spaces mode that is I suppose used mostly by npp users, maybe the difference in perception is what the Auto-Indent is doing. Actually I’m curious if anyone cares about trailing spaces at all (except when thinking about avoiding unnecessary bytes saved or implicit aesthetic reasons). The mere existence of “Trim trailing spaces and save” command probably partly answers this for many existing users, but I’m not sure about all.
Also interesting difference between Delphi editor and npp when the caret has some space after it and also meaningful text after the space. In the former after I press Enter the editor keeps the spaces and the text, but places the caret right below the character on the previous line so I have this space at the caret. In npp the caret goes to the start of the line and the meaningful text aligns to the line above.
The images below illustrates this
This is the state before I press enter in Delphi
Delphi_beforeEnter.png
… this is after
Delphi_afterEnter.png
This is before I press enter in npp
npp_beforeEnter.png
This is after
npp_afterEnter.png
I don’t know what kind is better, I’m more used to how Delphi handles it.