MAIL MANIA - Complexity Snatched from the Jaws of Simplicity

MacBookPro OSX 10.8.5
Mail Version 6.6 (1510)

If I try to create a new email by typing all appears to be normal.

But from time to time a block of text is suddenly surrounded by a rectangular line frame, with a X at one corner.
Clicking on the X makes the enclosed text disappear.

Clicking somewhere outside the frame makes the frame disappear.

It may be associated with a chunk of text pasted in from elsewhere, though I cannot prove that.

What is going on?

How can I disable this confusing "enhancement"?

Does the selected text by any chance have a date, or something that could be interpreted as contact information in it?

Does the selected text by any chance have a date, or something that could be interpreted as contact information in it?

Thanks to ian_c for above reply.
Well, I don't have familiarity with CONTACT requirements but I think it quite likely that chunks of text pasted into an email could contain a date.
That would seem to be a silly design feature if anytime a date appears the system assumes it is a CONTACT.
Can it be made inoperative?

One thing I did notice when searching the O'Reilly book was that WIDGETS seem to have the sort of framework and X mark which I described as making an uncontrolled and unwelcome appearance in a draft email.

I have no interest in or intention to use WIDGETS.
So again, is there a way of making them inoperative?

I notice that when I'm replying to someone with a Yahoo email address - drives me mad , but I can't see how to avoid it .

I'm on an MBP on 10.9.2 with MacMail 7.2

Not just contacts, but calendar events (and possibly reminders, I don't know). I can't replicate what you are describe. Could you give me a f'rinstance?