Steps for changing the heart icon, and the comment bubble in the news feed.

1. Download Inkscape. It's a freeware, and does very well working with .svg images.
2.Get these simple line icon sets.
  A. http://graphicburger.com/simple-line-icons-set-vol-3/
    1. unzip the file.
    2. navigate to the .svg 24px folder find "bubbles"
  B. http://graphicburger.com/simple-line-icons-set-vol-2/
    1. unzip the file.
    2. navigate to the .svg 24px folder fing "like"
3.Go to cpanel ow_themes/simplicity/images.
  A. Download the "miniic_set.svg" file.
    1. Save the file in a location you know.
    2. Go to where you saved the file, and make a copy of it 
       (i.e. "miniic_set_simplicity"). This is to have a     
       of the original file.
4.Open Inkscape
  A. Choose file/open
     1. Go to where you saved the "miniic_set.svg" file.
     2. Select the file, and click open.
5. You should now see the icon set. Two bubbles, and two    hearts.
  NOTE: Don't do anything with the icons yet.
6. Click on file/import
7. Go to where you found the 24px "bubbles" svg file.
  A. select the "bubbles" svg file, and click on open.
  B. Make sure the select tool is on in the top of the left      toolbar in Inkscape.
  C. Select the imported image, and right click.
  D. Choose copy (you'll need two of the icons)
  E. Right click on an empty area of the Inkscape page, and      choose Paste.
  F. You should now have two of the "bubbles" svg icons.
8.Repeat step 7 for the 24pz "like" svg.
9.Again; make sure the select tool is active.
  A. Click on the top bubble icon in the miniic_set.svg.
  B. with the icon selected; you should see some numbers at      the top of the page for X, Y, W, and H.
    1. Write those numbers down. They are the size and        position of the top icon.
10.With the top bubble icon still selected.
  A. Go to the Inkscape top menu.
  B. Select object/fill and stoke.
  C. Another box should open with RGB colors.
    1. Write the colors down for R, G, B, and alpha. This is        the color of the top bubble icon.
11.Repeat steps 9 and 10 for each icon in the"miniic_set.svg"
12.You can now drag the original icons out of the box.
13.Select one of the "bubbles" icons.
  A. Apply the size and position (X, Y, W, and H) that you      wrote down for the top icon.
    1. You should see the size, and position of the icon        change, and end up where the original icon was.
  B. With the icon still selected.
    1. Go to the Inkscape top menu and select object/fill and        stroke.
    2. Put the R, G, B, and alpha numbers you wrote down in        the color box.
    3. You should see the color of the "bubbles" svg change.
14.Repeat step 13 for all of the new icons.
15.Once done.
  A. Delete the old icons from the screen by selecting them,      and pressing delete ont your keyboard.
16.Save the file.
   Note: the file name still needs to be miniic_set.svg.
17.Upload the new miniic_set.svg file to your    themes/simplicity/images folder.
    1. You will get a message saying the file already exists.
    2. Click "Yes" to overwrite it.
18.Set Dev mode to true, and go to your site, refresh the    page, and you should see your new icons.