Currently Mattermost limits the length of posts to 16383 characters (https://mattermost.uservoice.com/forums/306457-general/suggestions/17368972-eliminate-4000-character-per-message-message-leng).

Most likely the limit is caused by the length of the TEXT field in supported MySQL, which is 65536 bytes. A UNICODE character can take up to 4 bytes, hence the safe limit:
65536 bytes / 4 = 16383,75 characters.

Using rich Markdown formatting, abundance of hyperlinks, one can reach the limit of 16383 characters in a research post.

To make it easier to scroll through the list, Mattermost collapses (hides) parts of long posts under "Show more" button/link, after showing first few lines.

Too make it even easier for the readers, spare their mental resources until they have time to study the long post, could you please add a custom TAG that would enable the author to collapse the post under "Show More" even earlier than default Mattermost setting, e.g. after the first line (= title), or after the short summary in the beginning?

Alternatively, if Mattermost team does not want to add custom TAGs that are not part of canonical Markdown (https://en.wikipedia.org/wiki/Markdown), add an option (checkbox) to a new post that would enable the author to specify that the long post content should collapse under "Show more" after the first/title line (assuming that it is shorter than default Mattermost character limit for the "Show more" feature)?

Thank you.