Markdown not working with biggish file

[David Tannenbaum]

I have a file that is just about 11k words long, and am trying to
convert it from Markdown to XHTML on OS X. I have so far tried three
different utilities, including Dingus, with no success.

I just went through page by page with Dingis, copying a little bit
each time, and discovered whtat I think is a length limit. No matter
what I typed beyond the limit, Dingus would not convert.

I did something similar with HumaneType 5 and an Applescript written for OS X.

Is there a limit on length?

Thanks,
David