Hello,

Drawing a rectangle in artist-mode going in the directions

 . down
 . left to right
 . up
 . right to left

introduces gaps unexpectedly at the final closing top side.  See,

=> http://sdf.org/~van.ly/img/emacs-30-0-91-artist-mode-rectangle-draw.jpeg .

To demonstrate,

 1. start, emacs -Q
 2. open buffer and activate artist-mode
    a. C-x b a RET
    b. M-x artist-mode
 3. draw line going down
    a. C-c .
    b. type +, type 40 .
 4. draw line going left to right
    a. C-c >
    b. type +, type 40 .
 5. draw line going up
    a. C-c ^
    b. type +, type 40 .
 6. draw line going right to left
    a. C-c <
    b. type +, type 40 .
    c. gaps are introduced between sequences of .

Expected result is a rectangle with no gaps on the top side.