I know what you mean.
Before the alpha and beta, we actually asked Japanese staff if they could change the number of characters you can type in chat.
And they said that it's not impossible, but it would be very difficult.
I understand that it could be very frustrating to break up a sentence while chatting, BUT surprisingly the number of characters you can enter is exactly same as the number in Japanese Alteil chat... which is 50 characters. (that includes spaces and commas) I logged in on Japanese Alteil, and counted this.
But because Japanese doesn't need a space after each word, and you can use kanji to make the length of one sentence shorter, it seems like you can type a lot more in Japanese.
About entering the text, hit enter twice
to enter the text.
I think this is also because this chat system is based on Japanese chat system.(in Japanese chat, enter once to change hiragana to kanji, and enter again to actually enter the text)
After bugs and glitches are fixed, we will ask everyone for suggestions or advice so we can improve Alteil.
Even if they said that it would be difficult to increase the max number of characters in chat, if many users feel that it should be more, they may give it a thought again. who knows...