Just to be complete, since some forums are in LTR direction while others are in RTL direction, the correct implementation must consider both cases, so that:

1) If the forum is in LTR direction and one wants to insert RTL text, we need:

<p dir="rtl"> ... </p>

2) If the forum is in RTL direction and one wants to insert LTR text, we need:

<p dir="ltr"> ... </p>

This way we cover all scenarios.

Honestly "my little forum" is really better then other forums I've used, including the most popular PHP forums; Yet most forums don't have the direction feature (that's one of the main reasons that I found "my little forum", since I was looking for a practical forum that also supports direction through BBcode).
What I mean is that adding this feature is another big advantage over many other forums.

For example, if I want to teach programming in Hebrew, then most of the text will be in English (LTR) of course, only some explanation will be in Hebrew (RTL).
Without the direction feature it is literally impossible - the text will turn into gibberish;
Look, the following sentence is completely out of order in LTR direction, i.e. it is displayed in reverse:

הפונקציה floor() מקבלת ארגומנט אחד: atom או sequence.

This is why we need the direction feature.

Thank you, shian.

Reference: https://www.w3schools.com/tags/att_global_dir.asp