This is completely according to me, what i feel, what i have experienced from my usage of Windows10Mobile build 10581 on my primary device. I feel that the Windows10Mobile has the worst keyboard ever. Some main reasons I feel that are:
1. Test recognition is bad.
2. While typing 'T' ,'Y' comes up instead (i didnt hav this problem on wp8.1)
3. Swipe keyboard has gone worst. I get 7/10 wrongs when i use swipe. Mainly when i swipe to type 'hi' it appears as 'ho'. (as said, never had this problem with wp8.1).
4. Emoticons (Emoji's) - they are actually a waste. Can't understand what some emoji means. Some look similar.,some r confusing, some can't be understood. Cant use in WhatsApp or other apps because it shows different emoji on WhatsApp and other apps
Refer : Open ur keyboard n see .. Frst Colum: Top n bottom emoji looks same.
I hope MS brings emoji similar to that in WhatsApp so we can use it directly from our keyboard. Extra new emoji that r not available in WhatsApp can be placed in another category.
5. As even Tom Warren and many other Tech websites reported, keyboards have rather interesting test suggestions.. Like "Can i touch your ...." (sry cnt upload pics/links here)
There are many other good features too::
1. New keyboards.
2. Cursor.
3. Listening (even though it doesnt work for me most f the time, takes time to turn on, sometimes).
4. Swipe on spacebar to change keyboard.
5. Clean Keyboard.