What version are you running?
2.0.12
What's the URL of the page containing the problem?
N/A
What steps will reproduce the problem?
1. Create a topic where the description is as below (see additional info).
2. Publish it.
3. Add a space to the line 'item three' (i.e., "3. item three ") and republish, which will produce a "review request changed" section.
What is the expected output? What do you see instead?
This raises an uncaught exception in Python.  If it does not do so immediately, try forcing a page refresh that does not hit the cache.
The end of the stack trace is:
      File "/usr/lib/python2.7/site-packages/reviewboard/reviews/markdown_utils.py", line 241, in iter_markdown_lines
        i += 1
    TypeError: unsupported operand type(s) for +=: 'instance' and 'int'
What operating system are you using? What browser?
OS X 10.10.2.  
Chrome Version 42.0.2289.0 canary (64-bit)
Please provide any additional information below.
Use the following as the description, minus the "--begin"/"--end" lines.
-- begin description --
1. item one -- change this item second time
/usr/bin #
* stuff here #
2. item two -- change this item
* stuff here
3. item three
3. wrong number
-- end description --