Placeholder messages display with HTML entities

[eloquence]

As of the December 6 nightly build, I see the following placeholders in Qubes when messages haven't been downloaded yet:

<Message not yet available>
<Reply not yet available>

Instead of the expected

<Message not yet available>
<Reply not yet available>

[kushaldas]

I can reproduce this.

[kushaldas]

This is due to the html.escape introduced via dcce99f commit. This helps to mitigate against any random random attack in the message text.

My suggestion is to just remove > and < characters from any such message. @eloquence @redshiftzero @emkll your thoughts?

[emkll]

related to #645

[eloquence]

I don't especially care about the use of these characters in the placeholder text (long term we want to use a different loading pattern anyway), but I do feel iffy about characters that should be safe when handled responsibly not working here. :/ And I do think we must resolve #645.