This is online.
Mental stability would involve grounded logic, balanced emotional regulation, and an absence of extreme volatility.
Repeated accusations & dramatic storytales built up inside your mind would signal a clear lack of mental stability.
If the reality of a poster stating that they had seen a post referencing two people seems to make you wobble then you may need to have a bit of a lie down.
Its a football forum.
I prefer to converse about the topics listed on the forum rather than deal with a wobbly person making childish accusations and comments.
Have a kitkat.