Yes, that is a perfectly valid optimization. However, with the introduction of the peephole optimizer in Axe 1.0, Axe will perform simple optimizations like that automatically so you don't have to.

Yeah this is more of a "Be lazy on purpose to make the parsing simpler with less error checking".  The right parentheis ) and } are identical in nearly every situation.  However, left parenthesis ( and { are obviously different.  When I said nearly, sometimes Axe checks for a specific kind of parenthesis so don't abuse this.  Also I could add error checking in later versions if there is ever ambiguity.

EDIT: For your specific example, the left parenthesis was the typo so it didn't work the way I presume you expected it to.

is there any way to draw a single column of pixels that's faster than drawing the same column with Pt-On(?

Maybe with a rectangle like Rect(X,0,96,1) or something (and if I didn't do any mistake) ?
Or maybe I didn't understand the question right -.-°

Also, I can't remember but do Bitmap clip ? Nvm, it does since 1.1.0

Yes, but it is said here

Redesigned Bitmap() command is clipped, faster, and works with any buffer.

So it should be ok

Rect() is a good amount faster at drawing horizontal or vertical lines than Line(). Pretty much, you'd only not want to use Rect() if speed is not critically important and you already use Line() in your program, but not Rect(). This would save some size by not having to include the 113-byte rectangle routine.

Method		Speed (cycles)		Code size (bytes)		Routine size (bytes)
Rect(X, and 0,+1, or 255)		3315		14		113
Line(X, and 0,X,63)		6094		17		140

What kind of data are we talking about?  Axe has built in Send() and Get() commands for sending bytes over the link port, but anything that was restricted to only using Port() to send bytes would basically be rewriting those commands.  Why do you need to use the Port command instead of using the Send() and Get() commands? 

Oh and the link port communication works across all Ti83+ through Ti84+SE if I remember correctly.