No, I don't think it would look odd at all. Getting the line horizontal and straight might be difficult but it could be really cool. I think adding the chair rail after you paint wouldn't be so difficult - and is something you could do if you still wanted to.

Thanks! Yes, we would add chair rails at a later date. This painting technique would just be to tide us over until we can get to that. And yes, I'm worried about getting the painter's tape perfect! That will probably be an adventure in itself.

It is a great look. My sister did this in an apartment and it looked wonderful. You'll get the lines down with little effort; a tape measure, pencil,and eraser. Measure bottom up.

Someone posted photos of their daughter's (?) tiny kitchen/dining area where they did a two-color paint job like this. It looked fantastic!

You can certainly paint two tones before the chair rail. Getting a straight line is very simple: use a level and draw a very soft pencil line. Or, use a laser level, make tick marks and tape along those. You will have 2 chances to obliterate those SOFT pencil marks, once when you paint upper, then again at the lower.
You should always remove the tape immediately. Blue tape in 1 1/2 inch works well, or you can use the green tape. Even though it says safe removal after one week, I would still remove asap.
Also, you can paint in the "white stripe" that mimics the chair rail (or whatever color your trim will be) as a temporary solution.
And, to get that straight line from the tape that you mentioned, gently burnish the edge of the tape running along the edge with your thumb. And when you are removing the tape, gently pull the tape at an angle, pulling it down and toward you. If you've seen the Home Depot commercial where they gleefully and quickly rip the tape off the wall may leave you with some repairs! Remember to let the paint dry before you tape over it, and you'll know it's wet because the tape won't stick.
And finally, you can alway re-tape an area to fix it if it's not perfect.
Hope this isn't too much info....

If you use the green tape (Frog Tape), I recently read that is a good idea to go over it with a damp sponge before you paint. The dampness of the sponge activates whatever it is that is supposed to prevent paint from bleeding under the tape.

It's never too much info! Thank you thank you!

I am going to put a chair/picture rail in a bedroom in a few weeks. It might even be higher than two-thirds up. I decided to paint the ceiling the same color as the upper section of the walls.

I really like paintergirls idea of the white stripe.

bbstx, I've never heard of that -- have you tried it? A good trick to prevent bleeding is to brush away from your paint line on a diagonal. If you brush towards your finished line, that will sometimes allow the paint to be pushed under the tape.
It seems to me that the water will encourage your paint to bleed. And, you also don't want whatever residue you are releasing to stay on the wall. A gentle burnish will create a tight seal, along with applying the paint away from your finished line.

My DD did this vertically, but it gives you an idea. A friend of mine did a horizontal two color treatment in her bedroom and it looked pretty neat.

This is the before
{{!gwi}}From Pictures

after
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{{!gwi}}From Pictures