It looks like the validation just occurs after the user is finished entering text. Adding autocorrect="off" can be used as a workaround for this issue.

I could not reproduce this issue.  Maxlength worked for me on 52 dev, tablet and desktop mode.  Could you take a video of the behavior you're seeing?

Following these steps I can reproduce this consistently:

1. Go to http://www.w3schools.com/tags/tryit.asp?filename=tryhtml_input_maxlength
2. auto-correction is enabled (moderate) and Gesture Typing is enabled
3. Flip Chromebook to tablet mode
4. Type letters with the on-screen keyboard

Result: it doesn't stop you from typing more letters than the maxlength of 10

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Part of what is going on here is that the input is being done in composition mode (as denoted by the underline beneath the text, which you may have turned off in your keyboard settings) and the text is not validated until the composition complete event is received. Personally, I find it really annoying that the auto-correction mode is being treated as a composition, but as noted you can disable this in your HTML by setting autocorrect="off" and autocomplete="off".

This works as intended for now. Maxlength doesn't restrict composition text.