The editor needs spellchecking - that's what I'm hearing
Most editors rely on adding spellcheck="true" attribute to their input or textarea so the browser takes care of it .
However slides.com isn't implemented like that so it could be tricky
underline things that are not words so we can correct them because honestly it gets annoying and a bit embarrassing too :(
AdminOwen (Owner, Slides) commented
This should already be enabled – the "spellcheck" attribute is supported by contenteditable elements and added when editing text in the Slides editor.
Tested this in Firefox and Chrome and things appear to be working. Here's what it looks like in Chrome: http://f.cl.ly/items/3g2R1X3A1o1r3A2Z0p2s/Screen%20Shot%202015-04-13%20at%2010.09.36.png