The limit is 500 characters. When the message length is > 500
, the following behaviour is triggered:

Unless we reduce the length until <= 500
, we won't be able to post it.
It seems that if we add a line break to our message, that is, pressing Shift + Enter to move the cursor to the next line, we can "bypass" the 500-char limit:

The shortcoming of this approach is that the MarkDown syntax will be automatically disabled. So, if we write e.g This is **a test**
, it will be handled literally instead of converted to "This is a test".
Update (Andrew's comment): When adding a line break, SE thinks you're going to upload a code listing, or similar. That's why Markdown is disabled.
When breaking a line, an extra button appears. If we click it, it will format the whole message as a code excerpt:

If the message/code is too long, it will be displayed partially:

Then we can click the see full text
link to expand it. :)
:)
a
's until one char before the crypticyour message is too long
info and then asked Python to count the whole amount for me.:)
I'm not a fan of chatrooms as an extension to a discussion in a question/answer; I usually like to follow them in loco. One advantage I see in chatrooms is that they are easier to follow, in the sense of context: you can reply to an specific sentence and everybody will be able to check the context.:)
+[chat]
(must be tagged with chat) andlimit
,character*
, orcount*
. I guess you could go ahead and start a feature request over there.:)
> 500
chars. I've detailed it in my answer.:)