Go for it mate - you won't be penalised, just maybe a few unpleasent replys
Inviting people who don't accept invites
You really should just leave them alone, but if you really want them to join your group, then by all means message them.

Right next to the input area it has this:
#2 - DO NOT SEND INVITES (for Tournaments or Groups/Teams) through these messages. If you want to send invites, please read:
Inviting Members to your Group/Team
Inviting Players to your Tournament
Failure to follow these rules may cause your account to be suspended or deleted.
Thank you for keeping Chess.com fun & friendly!

I once sent kleelof an invite by personal message. That's part of me being chewed up in his avatar. :-o

But what if that person is in 105 groups?
Perhaps that's why they aren't accepting group invites.
Besides, someone in that many groups probably isn't going to participate much if any in your group.

The reason I don't accept invites is because if I accept every one I get, it would be too many.
Why join another group that does the same as other ones do.
I see members with many groups what is the use if you don't participate in the group.
I have several right now and in one only a half a dozen members will play a match or vote chess.
Many of the highest rated members don't play any matches for the groups.They are just there for show.
Some times i see a post asking, "Is this group active? " I guess that is a group that I should drop.
IMHO

Hello!
Alot of people do not accept group invites- should I just send them a message to join my group? Will I be penalised for doing so?