User macros embedded in a line(or on it's own line) creates extra lines when going between wiki markup and rich text editor. It's similar but not the same to CONF-7628 which was resolved. In that new lines were created repeatedly.

1. Define User Macro
Macro Name: p
Macro Body: Macro has a Body (use unprocessed macro body)
Output: Macro generates html markup
Template: <b>$body</b>

2. edit in wiki mode

Some text before inline macro

more text after inline macro.

3. save and view

Some text before inline macro <b>Macro Body</b> more text after inline macro.

4. open in rte brings

Some text before inline macro

 more text after inline macro.

5. after save we got the following page view with 2 unwanted newlines before the macro and 2 unwanted macros after macro

Some text before inline macro

<b>Macro Body</b>

more text after inline macro.

When we use a user macro which generates wiki markup its even worse. Than we got unwanted newlines even in the wiki editor.