bug#19026: 24.4.50; rmail-summary-by-topic

[Glenn Morris]

Richard Stallman wrote:

> In rmail-summary-by-topic, if (rmail-simplify-subject) returns a
> string with a comma, that is taken as a comma-separated list of
> different things to search for.  Thus, it finds messages whose
> subject is just a part of this message's subject.

I wrote a FIXME comment about this 5 years ago:
  
  ;; FIXME "a string of regexps separated by commas" makes no sense because:
  ;;  i) it's pointless (you can just use \\|)
  ;; ii) it's broken (you can't specify a literal comma)
  ;; rmail-summary-by-topic and rmail-summary-by-senders have the same issue.

I suggest just dumping this "separated by commas" idea.
Ie, you would have to write "foo\\|bar" like in any other regexp.