[kh99]

I don't think it's a problem with enabling html. Apparently the javascript is suppose to run and convert the link into some html and something's not working. Do you by any chance have any mods installed that have to do with Twitter?

You could try this (as an experiment): Create a plugin using hook parse_templates and this code:

if (THIS_SCRIPT == 'showthread')
{
    $template_hook['footer_javascript'] .= '<script src="//platform.twitter.com/widgets.js" charset="utf-8"></script>';
}

then try posting just the blockquote part:

<blockquote class="twitter-tweet tw-align-center"><p>Marco Belinelli has received interest from the Bulls, Magic, Warriors and Knicks.</p>&mdash; Legion Sports (@MySportsLegion) <a href="https://twitter.com/MySportsLegion/status/225675484615294976" data-datetime="2012-07-18T19:36:43+00:00">July 18, 2012</a></blockquote>