For <h1>, I'd rather the message be "Don't use these" (as is noted at Perl Monks Approved HTML tags).

Note the red plus sign and lack of line number on the continuati­ons after wrapping is performed

Showing line numbers is not the default. For those fortunate enough to have a browser that supports soft hyphens (&shy;), "auto code wrapping" is a much nicer option and it doesn't produce any red plus signs (it can produce red hyphens but only when the wrapping happens in the middle of a long block of non-spaces).

(sometimes at unfortunat­e points, as seen in this instance.

There would likely be no "unfortunate point" when "auto code wrapping" is used but even for non-auto wrapping each user can pick their preferred line width so you shouldn't assert that the code will be wrapped at an "unfortunate" point in your specific example.

The main point for BR tags should probably also be "Don't use these". A note that </br> is a particulary bad idea might be warranted.

Update: By far the most common use of BR tags
is inappropriate.
So it seems more important to stress that
they not be used inappropriately
(to introduce line wraps within a paragraph --
I'm not sure why this is so commonly done).
Since examples were desired,
an example like Thanks,<br />Tye
would seem appropriate to me,
especially if it is noted that the use of BR tags
should be the exception and
normal paragraphs should be achieved via P tags.