When using the /say command the text that is displayed will often be cut off. I have uploaded a screenshot of what happens. In the screenshot you can see a sentence pasted into the world's chat next to the same sentence pasted using a /say command. It does not matter what you type, the sentence I used is just an example. The glitch also occurs if you type the sentence in instead of pasting it. The text will be cut whether you use a command block or the game's chat function. This happens on every world save and is not dependent on the options.txt or the resource pack.

This has been happening since 1.7.5-ish. I only reported it now because I noticed it wasn't fixed in the most recent snapshot.

I also took a short video showing off the glitch.
https://www.youtube.com/watch?v=GIwGQcXbSxY
(The sound is slightly off because I haven't configured Fraps)

Thanks for reading and have a nice day.