1) The cleaning up of codes:
<param></param> changed to <param />

<input /> changed to <input></input>

Everytime the system "cleans-up" the codes, it also eats up some codes after it, thus can cause errors or the other elements not rendering, example, <a href=""></a> becomes ef=""></a>.

I already turned off the XHTML strict but it still do its cleaning. I'm not sure, but maybe <input/> should be accepted?

Also happens with v2.x.

2) When sending trackbacks
Warning: Cannot modify header information - headers already sent in /public_html/blog/inc/_core/_template.funcs.php on line 174

Warning: Cannot modify header information - headers already sent by (output started at /public_html/blog/inc/_core/_template.funcs.php:174) in /public_html/blog/inc/_core/_template.funcs.php on line 182

3) Tags?
Just reposting it here since:

In my B2evo 3.1 test environment the tags are already aggregated in an aggregation blog.

~ http://forums.b2evolution.net/viewtopic.php?t=17707

The tags from my live 3.1-alpha ( http://laibcoms.asia/blog/ ) are not aggregate-aware.

4) Code Highlight Bugs
sample post:

[codespan]this
is
a codespan[/codespan]

[codeblock lang="" line="1"]
this is
a codeblock[/codeblock]

[codeblock lang="php" line="1"]
this is
a php codeblock[/codeblock]

[codeblock lang="html" line="1"]
this is
an html codeblock[/codeblock]

for v3.1-alpha HEAD
- codespan doesn't render (actually same with v2.x)
- the linenumbers and the horizontal line separating the each-line disappeared (as compared to v2.x) - it's now just a plain gray-box
- if the post is re-edited, the post turns into this (below), instead of retaining it's bbcode-style formatting

[codespan]this
is
a codespan[/codespan]

<!-- codeblock lang="" line="1" --><pre><code>
this is
a codeblock</code></pre><!-- /codeblock -->

<!-- codeblock lang="php" line="1" --><pre><code>
this is
a php codeblock</code></pre><!-- /codeblock -->

<!-- codeblock lang="html" line="1" --><pre><code>
this is
an html codeblock</code></pre><!-- /codeblock -->