I noticed that your rules about pixel art are very strict. But I can't find anywhere what is or what is not allowed.

Only rule I could find was in "Submission Rules":
6. Any art you post should be PIXEL ART! Pixel art implies that each pixel is placed by hand (no filters, paintbrushes, gradient fills, etc).

What does it mean anyway? That I can do everything what is not prohibited? Or that I must use what is allowed and everything else is prohibited?

I'd like to see document with a list of allowed or prohibited tools e.g. layers, resizing, copying selection, tile completion etc.

I find this very important and if there is document like this, please post it and consider puting it somewhere more visible.

What we want here, is that every pixel is placed by hand on the ending result.

Layers can be used, but not if you make them transparent because you would than not have selected all the colors yourself.

Resizing can't be used, because in the result the pixels are placed by the computer, who calculated where they would fit the best.

You can copy selections if you copy stuff that you have hand made too. It is just moving a group of hand placed pixels.

There is no complete list, but if you go with the idea:

I should have came with the same result if I used a pencil tool only

than its in most cases fine.

I think I understand the difference but I still think it is necessary to specify the "rules". Now it is fully in hands of admins who have their specialised tools and consider it ok.

I'll pick some of the techniques I think are not clear:

1. Color Selection - to change tone in whole picture or to move object. It is possible to go through each pixel and click on it :)
2. Transparent layers - to select and move object in foreground. That is IMHO possible by hand too but much more annoying.
3. Masking patterns. Pattern is handmade visible parts selection are also handmade.
4. Automation. I could copy and paste "handmade" bricks on the wall by hand but isn't it much easyer to let the script do it for you?
   
5. Drawing by selections and lasso tool. It is possible to draw that shape in pixels. But who can do that?
6. Brushes. You mean that 6x6 pixel circle shaped without anti aliasing is not allowed?
7. Resizing without filter. Resizing sucks a lot it destroys almost everything but i can rebuild my picture on that basis much easyer.
   
8. Having reference underneath your painting. You can eg. draw a grid and do the same grid in your painting and than mark key parts. but clicking on them in resized picture is much easyer.

I could probbably think of much more. The point is: There is no authorised specification. It means that it is the matter of individual opinion. So there is pixelart and pixelart by pixeljoint and i understand i have to asimilate their idea of pixelart. How can I when there is no specification? If you were all using MS Paint I'd not bother you.

1. You can change the colours using filters like contrast or saturation etc on something like photoshop, you can replace colours all you like.
2. Semi transparency is forbidden on pixeljoint because it makes the pieces hard to judge whether it's proper pixel placement or not and can greatly raise the number of colours without the artist realising. Full transparency is fine.
3. Not sure what this means entirely, but you can copy a dither pattern or w/e with transparency over the top of a flat colour no problem.
4. I see no reason why you couldn't do this without some script, it's not hard atall and takes little time if you do it efficiently.
5. As long as there is no auto-AA selecting pixels and filling them or w/e is fine, as long as everything you place is opaque.
6. I see no reason why that wouldn't be allowed.
7. You must state that you did this when you submit, so that other people can judge the piece from it. This is only as long as the piece resized is your own!
8. As above, you must state your references and whether you traced.

Hopefully that answers your questions. I think the other members may have been confusing when they said just pixel by pixel. This is of course not true, you can use a non-AA line tool or shape tool, as well as fill tools etc. Spraycan is greatly frowned upon because it delivers no pixel accuracy, you must fix it after use (but why would you use it anyway in that case?). As long as the tuning is on a pixel-by-pixel level basically.