Uhm, so I had a dozen something of original (source) images deleted in favor of previews (with larger file size).

Can I get a definitive answer on how such cases are handled,
Should I upload original image or should I upload generated preview image?

Images generated for preview are always larger in file size, but they are not better, they are worse.

I have actually noticed how you have been trying to upload original versions of images but them getting flagged as inferior to pixiv generated previews of images. Would actually like someone to double check those removed posts as most were original images instead of pixiv previews already here.

This isn't pixiv issue only either, many sites love to hide original files in places.
There's even PSA forum topic for this: https://e621.net/forum/show/169987

Yes, original images are the ones that should be uploaded and those are the ones that should stay. You can read unofficial guidelines here, basically higher quality file is to be stayed, this should include original files even if filesize is lower, unless the file has been here for really really long time.

If you are uploading image that is original instead of preview, make sure you flag the earlier post as inferior and make it super clear for everyone that what is the case (keep image url in source, so it can be checked if it's original or preview and put in description something like "original image to replace pixiv preview posted earlier" or similar).

DelurC said:
Uhm, so I had a dozen something of original (source) images deleted in favor of previews (with larger file size).

The ones that got deleted were the censored versions. The uncensored ones from Tumblr were kept. ...and besides, you flagged those uploads yourself. :/

Unless you're talking about something older?

Genjar said:
The ones that got deleted were the censored versions. The uncensored ones from Tumblr were kept. ...and besides, you flagged those uploads yourself. :/

Unless you're talking about something older?

There are some originals that were deleted while being the same.
And while we're at it, are censored posts considered duplicate?

DelurC said:
There are some originals that were deleted while being the same.

I have no way of telling which ones those would be, and I'm not about to check all of them manually. Dmail me a list of the disputed ones and I'll take a look.

And while we're at it, are censored posts considered duplicate?

Depends. If it's just an edit by someone else, we tend to keep both.
But if both versions are by the artist, there's rarely any need to keep the censored version.

I just checked first page and found only two, must have been an error then, seemed odd to have a xy amount deleted.
post #1009796 and post #1009795

Also another question, why can't I check url #http://i1.pixiv.net/c/1200x1200/img-master/img/2016/09/06/05/45/28/58843352_p0_master1200.jpg with harry.lu (I understand original can not be because it requires referer)
With url #http://i1.pixiv.net/c/128x128/img-master/img/2016/09/06/05/45/28/58843352_p0_square1200.jpg works but its useless.