Subtitles: wrong implementation of html tag matching

Currently it is like this:

<s>this doesn't work
<i>this work
<x>These are matched and hidden while they are different so it is wrong</y>

It should follow more this schemes:

1) Closed tags are hidden (both supported and unsupported/invalid), closed tags: <i></i> and <gggg></gggg>
2) Tags NOT opened are showed as text and ignored (both supported and unsupported/invalid), tags NOT opened: </i> and </gggg>
3) Tags NOT closed (<i> and <gggg>):
    * Supported tags are hidden and they do what they should do (since some subtitles may incorrectly have html tags not closed)
    * Unsupported/invalid tags are showed as text (because they aren't closed)

Example, this:

1
00:00:02,001 --> 00:00:16,001
<b>Both line should be bold
but the wrong closing tag should be showed</s>

Should be displayed:

'''Both line should be bold

but the wrong closing tag should be showed'''

Look from 00:01:00 to 00:01:08 of http://anonym.to/?http://ale5000.altervista.org/other/SubRip_subtitles_capability_tester.zip